THE COTYLOPHOEA. 327 



and tlie tendency to ossification in the pelvic ligaments and 

 of the aponeurosis of the, muscles of the back, in adult males. 

 Finally, the navicular, cuboid, and ectocuneiform bones in the 

 tarsus are all anchylosed together. If, as is probable, XipJio- 

 don is one of the Tragulidoe, the group has existed since the 

 eocene epoch. 



b. The Cotylophora are, like the preceding group, unguli- 

 grade, but the outer metacarpals and metatarsals are incom- 

 plete at their proximal ends, and the middle ones are early 

 imchylosed into a cannon-bone. The malleolar bone is always 

 distinct. The navicular and the cuboid bones of the tarsus are 

 anchylosed together, but rarely with any other tarsal bone. 

 The premaxilla is devoid of teeth in the adult. The stomach 

 has the structure which has been described as typical. 



The blood-corpuscles are circular, and may have a diametei" 

 of as little as -g-j^j-j- of an inch. 



The foetal villi are gathered together into bunches or co- 

 tyledons, vrhich may present either a convex or a concave face 

 toward the uterus. They are received into persistent eleva- 

 tions of the mucous membrane of the uterus, the surfaces of 

 which present a reverse curvature. 



All the Gotylophora except Moschus, the true Musk Deer, 

 are provided with horns, but these horns are of two kinds. 

 The bony core, in the one case, is ensheathed in a strong horny 

 epidermic case ; while, in the other, the epidermis of the integ- 

 ument which covers the core does not become so modified. 

 In the former kind of horn, the core becomes excavated by the 

 extension into it of the frontal sinuses, whence the Ruminants 

 which possess such horns are not unfrequently called Gavi- 

 comia (Antelopes, Sheep, Goats, Oxen). As a general rule, 

 the horny sheath persists throughout life, growing with the 

 growth of the core. But in the remarkable Prong-horned 

 Antelope of North America {Antilocapra), the homy sheath 

 is annually shed and replaced by a newly-formed one. 



Of the second kind of horn, or that which acquires no homy 

 sheath, there are also two kinds. In the Girafi"e, the horn- 

 oores are attached over the coronal suture, at the junction of 

 the frontal and parietal bones, with which they are not anchy- 

 losed ; they persist throughout life, and are always covered 

 by a soft and hairy integument. 



In the Deer, on the other hand, the frontal bones grow out 

 into solid processes, which are, at first, covered by soft and 

 hairy integument ; generally they are developed in the male 

 sex only, but both sexes have them in the Reindeer. The 



