OCR Text |
Show 360 DR. J. MURIE ON T H K [May 26, The basioccipital (Bo) is an inch broad behind, continued forwards with a steady reduction of breadth to the junction of the basisphenoid (Bs). There is a trace of a middle longitudinal ventral crest with wide muscular concavities on either side of it. The so-called posterior tubercles of the basioccipital are badly represented, though not perfectly obsolete as are the anterior tubercles. No shadow of doubt crosses my mind as to the pattern of the entire occipital bone, which is modelled precisely as in the Cervidae. The supraoccipital in the Antelopes is protuberant and convex ; the condyles have a more rounded mesial division ; either the posterior or anterior tubercles of the basioccipitals are well developed, the latter often very convex and prominent. In Ovidee and Capridee the basioccipital is flat but wide, quadriform, with pronounced fore-and-aft tubercles. The superocciput in Oxen offer some resemblances to the Deer and Prongbuck, but their basiocciput is distinctly different in having well-developed tubercles and a deep groove between them. There is a moderate narrowing forwards of the basisphenoid (Bs) in proportion to the breadth of its occipital end, and the bone agrees with many Deer and some Antelopes in the amount of convexity and lateral guttering. The pterygoid plates and processes are thin, widely apart, and with obsolete hamular processes. The alisphenoid is narrow fore and aft, and the sphenoidal fissures are of great size. The orbito-sphenoid plates are less depressed or scooped out than in most similar- sized Ruminants ; and as a consequence the orbit appears less deep than in many forms. The horizontal plates of the palatines (Pl) together form about the hinder fourth area of the entire hard palate. Their sinuous maxillo-palatine suture presents a wide arch, interrupted by wide posterior palatal foramina. Between the last molar, retrocedent an-trial process, and the wall of the posterior nares there is an unusually deep notch or interspace. The vomer is very stout, the inferior turbinate bones uncommonly long and inflated. Three skulls of Antilocapra americana in the British Museum vary so very little as regards dimensions, that I have thought the one obtained from the Gardens might suffice, as underuoted, to indicate general admeasurements. inches. Extreme length 11*3 Extreme breadth, viz. diameter at posterior rim of orbit .... 5-7 Diameter opposite hinder ends of premaxillaries 2*0 Highest perpendicular without mandible, mid-horns 3*6 Height (or depth), vertical, with penultimate upper molar . . 3*3 Greatest length of nasals 4*2 Distance from anterior upper premolar to tip of premaxillaries 3*7 Length of row of grinding-teeth 2*9 Distance between occipital foramen and semilunar border of the posterior nares 3-2 Diameters of orbit I'7 |