Zoological Society. 481 



to above * . The considerable upward extension of the masseteric ridge 

 upon the os malse beneath the orbit seems also characteristic of the 

 Ruminants, as well as the bifurcation of the orbital ala of the sphenoid, 

 which sends a branch forwards for a considerable distance, often so 

 far as to articulate with the lacrymal bone. They also diifer from 

 the Hog-tribe in having, hke the Perissodactyla, a distinct styloid pro- 

 cess, emanating from the mastoid bone, partly enclosed by a portion 

 of the tympanic, and with a truncated extremity, to which one of the 

 angles terminating the "lesser comu" or stylo-hyal bone is attached ; 

 while in the Hog-tribe this process is so completely pressed between 

 the paroccipital process and the auditory bulla, that in most cases it 

 does not seem to exist. 



It will perhaps be most convenient to assign the rank of " family" 

 to the four generally received subdivisions of this ancient order, 

 although the osteological differences which they present are very 

 slight ; such few as I could find in the skull I will now point out. 

 In the Camels and Llamas, the articulation of the lower jaw differs 

 from that of Ruminants in general, in having a distinct eminentia ar- 

 ticularis, separated by a fossa not having the character of an articula- 

 ting surface from the post-articular process, upon which is another 

 facet ; the condyle of the jaw having likewise two articulating surfaces 

 placed at right angles with each other. There is also a marked pe- 

 culiarity in the auditory bulla, since the outer wall of the vaginal 

 process forms a deep, thickened, vertical plate, burying the styloid 

 process between it and the opposite part of the bulla. On looking at 

 the casts of the skull of the Anoplotherium existing in our museums, 

 I perceive, immediately under the meatus auditorius, a strong vertical 

 process, apparently the outer edge of this lamelliform expansion, the 

 remainder being concealed in the matrix. I fully concur in Professor 

 Owen's reasons for considering the Anoplotherium as a ruminant, and 

 this indication of character, in addition to the many resemblances 

 which authors have pointed out, renders it probable that this early 

 representative of the Artiodactyla belonged to the family Camelidts. 

 The existing members of this family also most approach the Anoplo- 

 therium in the form of the ascending ramus of the lower jaw, and the 

 strongly-marked notch which bounds the angular process above. 



I am glad to find that I have the sanction of Professor Owen's 

 opinion in referring the Merycopotamus to the ruminant division, 

 since on examining the specimens in our National Museum, I find 

 that in addition to the form of the teeth, which if taken alone are not 

 always to be depended on, all the essential characters of the skull are 



* In the Hippopotamus the pterygoid ridge runs inwards and even a little back- 

 wards, and then forms a slight angle at the point of junction with the pterygoid 

 process, which then runs downwards and forwards, so that the outer wall of the 

 fossa exists as in the allied forms, while, as I have before observed, it is the inner 

 one which is wanting. I must again refer to the remarkable osseous bulla within 

 the orbit of this animal, since I find that the same thing exists, though of much 

 smaller size, in most ruminants ; in many skulls it is broken away, and when re- 

 maining it so Ues upon the " tuberosity" or posterior termination of the alveolar 

 process of the maxillary bone as to appear at first like a part of it. It opens into 

 the nose and antrum maxillare, and has no connection with the lacrymal apparatus. 

 Ann. ^ Mag. N. Hist. Ser. 2. Vol. vi. 32 



