OCR Text |
Show 364 PROF. W. H. FLOWER ON THE EDENTATA. [Apr. 18, mecophaga and Megatherium ; but in the peculiar form and ankylosis of some of the cervical vertebrae, common to all existing members of the family, it stands apart from all other Edentates. In the presence of a clavicle it resembles the other American forms ; but it differs in the shape of the scapula, and in the existence of a third trochanter to the femur. The structure of the extremities, especially the manus, presents many modifications, some of which are quite comparable to, though not identical with, those of the Myrmecophagida. The reproductive organs differ in the presence of a largely developed copulating organ in the male, and of a simple vagina of corresponding length in the female; these, as long ago suggested by Professor Owen, appear to be correlated with the difficulties which would otherwise be interposed to sexual congress by the arrangements of the dermal armour, and which of course do not occur in the Sloths and Anteaters. The testes are still abdominal, though not in the same position; and the penis, notwithstanding its size, wants (as pointed out by Morrison Watson l) both the glans and bulb, generally formed in mammals by the corpus spongiosum. The uterus is as simple, or nearly so, as that of the Sloths and Anteaters ; and there is no reason to suppose, from what is at present known, that the placentation differs in principle from that of those families ; for if deciduate, whether the whole mass assumes an oval, discoidal, or bell-shaped form is only a matter of detail. The Armadillos, then, have undoubtedly near affinities to the other American Edentates, and are probably members of the same group, though not so nearly related to either of the other families as they are to each other, and are moreover remarkably specialized in a particular direction. The Glyptodonts form an allied group, agreeing in most essential features, but also presenting some very singular special modifications. Lastly, Orycleropus is a form in most respects perfectly apart from all the others. The structure of its teeth alone would almost entitle it to be placed in an order by itself, were it not for the practical inconvenience of doing so. Its vertebral column is formed on the normal type of mammals. Its limbs also present comparatively few specializations ; but it resembles the Armadillos in possessing a third trochanter to the femur. Its digestive organs are also comparable to those of the Armadillos, as its mode of feeding is similar. But its reproductive organs, both male and female, and placentation are formed upon a principle unknown in other Edentates, or, in combination, in other mammals. The testes, in a specimen I once examined, were inguinal, though they appear to descend, at all events temporarily, into a scrotum; but the penis is almost as small as in the Great Anteater. The uterus is more bicornuate than in Manis, the two lateral chambers opening separately into the vagina, as in some Rodents. The placenta, as described by Prof. Turner, is broadly zonular; but whether deciduate or not is at present undetermined, probably the latter. As Balfour remarks, this type of placenta is capable of being easily derived from that of Manis, 1 P. Z. S. 1878, p. 677. |