The Cambridge Natural History Part 43

FAM. 4. POTAMOGALIDAE.--This family contains two genera, _Potamogale_ and _Geogale_.

_Potamogale velox_ is a West African animal, which though an Insectivore has the habits of an Otter. It is "somewhat larger than a stoat." The upper surface of the body is dark brown, the belly brownish yellow. It has a flat head and a long tail like the Stoat, but the tail is laterally compressed and very thick. The eyes are very small; the nostril has valves. The toes are not webbed; but the second and third toes are united for the whole length of their first phalanges. Along the outer side of the foot is a thin extension of the integument. In swimming the feet are drawn up along the body, hence webbing would be of no use; but the thin flattening prevents the edge of the foot from acting as a hindrance to the motion of the animal. M. du Chaillu describes it as catching fish, which it pursues with extreme rapidity in the clear mountain streams it frequents; but Dr.

Dobson, remarking that no stomachs have been examined, thinks that water insects are more probably its prey. It is not known whether the animal possesses a caec.u.m. The tooth formula[389] is I 3/3 C 1/1 Pm 3/3 M 3/3. The animal is exceptional among the Insectivora in having no clavicles.[390]

There are sixteen ribs; there is no zygomatic arch, and the pterygoids converge posteriorly.

_Geogale_, with one species, _G. aurita_, is a small representative of this family from Madagascar. It has only thirty-four teeth. When better known it may be necessary, thinks Mr. Lydekker, to make this animal the type of a separate family. The tibia and fibula are distinct, not confluent with one another as in _Potamogale_.

FAM. 5. SOLENODONTIDAE.--This family contains but a single genus. {514}

_Solenodon._ This genus, including two species, one from Cuba, the other from Hayti, was at one time referred to the Centetidae. It offers, however, numerous points of difference from the members of that family with some general points of agreement. Possibly its isolation in the two West Indian islands mentioned is comparable to the isolation of the Centetidae in Madagascar; they are both survivors of an ancient group of Insectivores extinct elsewhere. _Solenodon_ has nearly the complete dent.i.tion. It has lost only one premolar, and has therefore forty teeth in all. The formula is thus I 3/3 C 1/1 Pm 3/3 M 3/3. It also differs from the Centetidae in having only two inguinal mammae instead of both inguinal and thoracic; the p.e.n.i.s of the male does not project from a cloaca, but lies forward. On the other hand, the molars have their cusps arranged in the [391]-fas.h.i.+on of the Centetidae, a fact, however, which, in the opinion of some, merely points to an ancient trituberculism not indicative of special affinity. It has, moreover, no zygoma in the skull, and there is no caec.u.m. Dr. Dobson has furthermore tabulated a number of differences in muscular anatomy between the two families. _Solenodon_ has a long naked tail. The snout, always developed in Insectivores, is extraordinarily long in this genus. It is a furry, not a spiny animal. _S. cuba.n.u.s_ is liable to fits of rage when irritated, a feature which it has in common with Shrews and Moles; it is also stated to have the ostrich-like way of concealing its head in a crevice, "apparently thinking itself then secure." But nothing is known of the genus in a wild state.

FAM. 6. CHRYSOCHLORIDAE.--This family contains only the genus _Chrysochloris_, comprising some five species, all natives of Africa south of the equator. The scientific name of the genus, and also the vernacular name Cape Golden Mole, are derived from the beautiful iridescent hairs which are intermingled with softer and non-iridescent fur. _Chrysochloris_ has [392]-shaped cusped teeth like those that are possessed by the Centetidae and Solenodontidae. In the skull as in the Macroscelidae, etc., but not in the Centetidae, there are complete zygomata. They are Moles in habit, and the eyes are covered with skin; the ears, moreover, have no conches. The teeth are forty or thirty-six in number, the reduction being caused by the losing of a molar in those forms which possess the smaller number.[393] It is interesting to notice that the {515} adaptation to a digging life is brought about in quite a different way from that of the true Moles (_Talpa_). In the latter the fore-limbs are changed in position by the elongation of the manubrium sterni, carrying with it the clavicles, which are extraordinarily shortened (Fig. 251). In _Chrysochloris_, on the other hand, the same need (_i.e._ that the limbs project as little as possible from the sides of the body, while the length of the limbs is retained, and the leverage of the muscles unaffected) is provided for by a hollowing out of the walls of the thorax, the ribs and the sternum being here convex inwards. The sternum and the clavicles are not modified. The tibia and fibula are ankylosed below. In the ma.n.u.s, moreover, there are but four digits, of which the two middle ones are greatly enlarged. In the Moles there are five fingers, and all are enlarged; there is, too, a great radial sesamoid bone, which is as good as a sixth finger (which, indeed, it is considered to be, in common with similar structures in other animals, by some anatomists). The foot has only four toes.

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FIG. 249.--Golden Mole. _Chrysochloris trevelyani._ A, Lower surface of fore-foot. . (After Gunther.)

FAM. 7. MACROSCELIDAE.[394]--This family contains three genera, all of them African in range, and mainly Ethiopian.

_Macroscelides_, the Elephant Shrews, are jumping creatures of Shrew-like appearance, combined with a Marsupial look. Both radius and ulna, and tibia and fibula, are ankylosed. There {516} are five fingers and toes. There is a caec.u.m as in but few Insectivores. The tooth formula, as revised by Thomas,[395] is I 3/3 C 1/1 Pm 4/4 M 2/(2 or 3), the total number being thus forty or forty-two. There are several species of this genus.

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FIG. 250.--_Rhynchocyon chrysopygus._ . (After Gunther.)

_Rhynchocyon_ and _Petrodromus_ differ from _Macroscelides_ in not having such long hind-legs. The dental formula of the first is I (1 or 0)/3 C 1/1 Pm 4/4 M 2/2 = 34 or 36, of the latter I 3/3 C 1/1 Pm 4/4 M 2/2 = 40. In _Petrodromus_ the toes are reduced to four; in _Rhynchocyon_ there are only four digits in the ma.n.u.s as well as in the pes. This animal, as its name implies, has a longish proboscis, which can be bent, and is really very like a miniature Elephant's trunk, and also like that of the Desman (_Myogale_). It has thirteen pairs of ribs, and a well-developed caec.u.m.

Dr. Gunther has pointed out that in _Petrodromus tetradactylus_ the hairs of the lower part of the tail are stiff elastic bristles 5 mm. long, with a swelling at the free tip. The use of this singular modification is not at all apparent. _Pseudorhynchocyon_, of European Oligocene, is believed to be related to this family.

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FIG. 251.--Sternum and sternal ribs of the Common Mole (_Talpa europaea_), with the clavicles (_cl_) and humeri (_H_); _M_, Manubrium sterni. Nat.

size. (From Flower's _Osteology_.)

FIG. 252.--Bones of fore-arm and ma.n.u.s of Mole (_Talpa europaea_). 2.

_C_, Cuneiform; _ce_, centrale; _l_, lunar; _m_, magnum; _p_, pisiform; _R_, radius; _rs_, radial sesamoid (falciform); _s_, scaphoid; _td_, trapezoid; _tm_, trapezium; _U_, ulna; _u_, unciform; _I-V_, the digits.

(From Flower's _Osteology_.)

FAM. 8. TALPIDAE.--This family is confined to the Palaearctic and Nearctic regions, or practically so, being fairly equally {517} distributed as regards genera; a Mole just gets over the boundary into the Oriental region. The genus _Talpa_ is entirely Old World in range, and includes several species, of which the Common Mole, _T. europaea_, is the best known. There are forty teeth, one of the molars of the full mammalian dent.i.tion not being represented. In the milk dent.i.tion there is an additional premolar, not represented by a successor in the permanent dent.i.tion. The formula is thus I 3/3 C 1/1 Pm 4/4 M 3/3. There are no external ears, and the eyes are rudimentary; the soft silky fur is familiar to everybody. The sternum has a strong crest, a.s.sociated with a powerful development of the pectoral muscles, so necessary to a burrowing animal.

The animal, it is hardly necessary to state, lives underground in burrows excavated by itself, which have not, it has been stated, the elaborate and, it appears, fanciful shape a.s.signed to them by many writers. At times Moles appear above ground. {518} Their princ.i.p.al food consists of earthworms, and it may not be out of place to quote Topsell's quaint account of their pursuit of the annelids: "When the wormes are followed by molds (for by digging and heaving they foreknow their owne perdition) they fly to the superficies and very toppe of the earth, the silly beast knowing that the molde, their adversary, dare not followe them into the light, so that their wit in flying their enemy is greater than in turning againe when they are troade upon." It has lately been said[396] that Moles store up earthworms for consumption during the winter, biting off their heads to prevent their crawling away.

_Scalops_, an American genus, is a Mole-like creature of largely aquatic habits, as its webbed hind-feet show; it has a short, naked tail.

Apparently, like the Shrews, it has no lower canines.

_Condylura_, another American genus, is called the Star-nosed Mole on account of a curious radiating structure at the end of the snout.

_Myogale_, the Desman, is still more aquatic in habit, and connects the Moles with the Shrews, though, as in many of the former, it has lower canines. It has webbed hind-feet and a long tail. One species occurs in the Pyrenees, the other in Russia. A few other genera (_Urotrichus_, _Uropsilus_, _Scaptonyx_, _Dymecodon_, _Scapasius_, _Perascalops_) belong to the same family.

FAM. 9. SORICIDAE.--The true Shrews have a much wider range than other families of the present order. In the Palaearctic region are found _Sorex_, _Crossopus_, _Crocidura_, _Nectogale_, _Chimarrogale_. The first is also Nearctic, and reaches Central America. In the Ethiopian region is the single peculiar genus _Myosorex_, but _Crocidura_ occurs there also.

_Blarina_ and _Notiosorex_ are "Sonoran" in range; _Soriculus_ Oriental.

_Crocidura_, _Anurosorex_, and _Chimarrogale_ also enter this region.

_Sorex_ has teeth tipped with reddish colour, its dental formula being, according to Mr. Woodward's recent researches, I 3/(2 or 3) C 1/0 Pm 3/1 M 3/3 = 32 or 34.

As compared with other Insectivores, therefore, the most remarkable fact found throughout the family is the absence of the lower canines. In addition to this the genus may be known--the family indeed--by the large size of the first pair of incisors. In the above formula it is possible, thinks Mr. Woodward, that there may be errors; he is not certain whether the supposed {519} upper canine may not be a fourth incisor, and whether the first premolar may not be really the canine. Another peculiar feature about the dent.i.tion of _Sorex_ is the suppression of the teeth of the milk dent.i.tion, which are functionless, and probably uncalcified. The genus _Sorex_ is terrestrial. The tail is long and covered with hairs. There are two species in this country, _S. vulgaris_ and _S. minutus_. The former is the Shrew of legend and superst.i.tion; and it is no doubt the species that has lent its name to the more untameable members of the softer s.e.x, though it is the males which are especially pugnacious. As to legend, everybody has heard of the shrew ash whose leaves, after a Shrew has been inserted living into a hole cleft in the tree, are a specific for diseases of cattle, caused by the Shrew itself creeping over them.

The Rev. Edward Topsell, author of _The Historie of Four-footed Beastes_, who defends his veracity by a.s.serting that he does not write "for the rude and vulgar sort, who being utterly ignorant of the operation of learning, do presently condemne al strange things," says of the Shrew that "it is a ravening beast, feigning itself gentle and tame, but, being touched, it biteth deep and poysoneth deadly. It beareth a cruel minde, desiring to hurt anything, neither is there any creature that it loveth, or it loveth him, because it is feared of all." It is probable that all this rustic feeling is due to the powerful effluvium which the Shrew undoubtedly emits.

_S. minutus_ has the distinction of being the smallest British mammal; it is scarcer than the last. This form is found upon the Alps, as is also the peculiarly Alpine species _S. alpinus_, which inhabits the Alps, Pyrenees, Carpathians, and the Hartz.

_Crossopus fodiens_, the Water Shrew, has also brown-stained teeth. It is not uncommon in this country, and lives in burrows excavated by the sides of the streams which it affects.

Besides these two genera, _Soriculus_, _Blarina_, and _Notiosorex_ have red-tipped teeth. In _Crocidura_, _Myosorex_, _Diplomesodon_, _Anurosorex_, _Chimarrogale_, and _Nectogale_ the teeth are white-tipped. These are all the genera of the family allowed by the late Dr. Dobson in a review of that family.[397]

_Chimarrogale_ and _Nectogale_ are aquatic genera. The former {520} consists of a Himalayan and Bornean, and of a j.a.panese species, which have not webbed feet, but have a tail with a fringe of elongated hairs.

_Nectogale elegans_ is one of the characteristic animals of the Thibetan plateau. It has webbed feet. The teeth are as in _Chimarrogale_ I 3/2 C 1/0 Pm 1/1 M 3/3.

The other genera are terrestrial in habit.

SUB-ORDER 2. DERMOPTERA.

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FIG. 253.--_Galeopithecus volans._ 1/3. (After Vogt and Specht.)

The family GALEOPITHECIDAE contains but one genus, which has been at times referred to the Lemurs, to the Bats, or has been made the type of a special order of mammals. It is better to regard it as an aberrant Insectivore--so different indeed from other forms that it requires a special sub-order for its reception. {521}

_Galeopithecus_[398] inhabits the Oriental region. It is a larger animal than any other Insectivore, about the size of a Cat, and has a patagium extending between the neck and the fore-limb, between the fore-limb and the hind-limb, and between the hind-limb and the tail. This patagium is abundantly supplied with musculature, but the fingers are not elongated as in the Bats for its support. In the degree of its development, however, the patagium of this creature is midway between that of _Sciuropterus_ on the one hand, and the Bats on the other. It presents many remarkable features in its organisation. The brain is like that of the Insectivora in the exposure of the corpora quadrigemina by the slight extension backward of the cerebral hemispheres; but its upper surface is marked by two longitudinal furrows on each side, a state of affairs (in combination) which is unparalleled among the Mammalia. The teeth are peculiar by reason of the singular "comb-like" structure of the lower incisors. This, however, is an exaggeration of what is to be found in _Rhynchocyon_ and _Petrodromus_, while the same style of tooth, though not so highly developed, characterises certain Bats. The Tupaiidae and certain Lemurs show what Dr. Leche regards as the beginning of the same thing. As in _Tupaia_ also there is an indication of the characteristically Lemurine sublingua. The stomach is more specialised than in other Insectivores, the pyloric region being extended as a narrowish tube. There is a caec.u.m. A peculiarity of the intestinal tract is that the large intestine is longer than the small.

ORDER XII. CHIROPTERA.

We may thus define the Bats:--Flying mammals, with the phalanges of the four digits of the hand following the pollex greatly elongated, and supporting between themselves and the hind-limbs and tail a thin integumental membrane, which forms the wing. The radius is long and curved; the ulna rudimentary. The knee is directed backwards, owing to the rotation of the limb outward by the wing membrane. From the inner side of the ankle-joint arises a cartilaginous process, the calcar, which supports the interfemoral part of the wing {522} membrane. The mammae are thoracic; the placenta discoidal and deciduate. The cerebral hemispheres, which are smooth, do not extend over the cerebellum.

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FIG. 254.--Barbastelle. _Synotus barbastellus._ . (After Vogt and Specht.)

This large order of mammals was once placed with the Primates. There is no doubt, however, that they form a perfectly distinct order; no knowledge of fossil forms in any way bridges over the gap which distinguishes them from the highest mammals. The most salient feature in their organisation is clearly the wings. These consist of membrane, an expansion of the integument, provided with nerves, blood-vessels, etc., which mainly lie stretched between the digits 2 to 5. These digits themselves, which are enormously elongated, act like the ribs of an umbrella, and when the wing is folded they come into contact. Besides this part of the flying apparatus there is a tract of membrane lying in front of the arm, which corresponds to the wing membrane of the bird, but which in the Bats takes quite a subordinate place. In the bird, on the other hand, there is a metapatagium, which is the main part of the wing of the Bat. It seems just possible that in _Archaeopteryx_ the metapatagium was more Bat-like. Furthermore, a steering membrane, like that which fringes the tail in some Pterosaurians, lies interfemorally in Bats, and includes the whole or a part of the tail.

The pollex takes no share in the wing, but projects, strongly armed with a claw, from the upper margin.

The bones of this order of mammals are slender and marrowy; they are thus light, and subserve the function of flight. A most remarkable feature among the external characters of the Bat tribe is the extraordinary and often highly complicated membranes which surround the nostrils. These are at least often {523} more strongly developed in males than in females, and may perhaps be partly relegated to the category of secondary s.e.xual characters.

But it seems that they have also an important tactile function, and enable the creatures to fly without touching bodies which intrude themselves upon their way. The ears, too, are frequently very large, and it may be supposed that the sense of hearing is correspondingly acute. In the common Long-eared Bat of this country, the ears are not greatly inferior in length to the head and body of the animal combined. The ears are of every variety of shape, and offer characters which are valuable in the systematic arrangement of the members of the order.

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FIG. 255.--Skeleton of Flying Fox. _Pteropus jubatus._ 1/8. (After de Blainville.)