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XVI. Researches wjjon the Anatomy of the Pinnipedia. — (Part III.) Descriptive Anatomy 

 of the Sea-lion (Otaria jubata). By Jajies Mukie, M.B., F.L.S., F.G.S., &c., 

 late Prosector to the Society. 



Bead Deoember 6th, 1870. 



[Plates LXXV.-LXXXII.] 



Contents. 



I. The Skeleton and Cranial changes, p. 501. 

 II. The Nervous System, p. 517. 



III. Sensory Apparatus, p. 534. 



IV. The Vascular System, p. 535. 



V. Hyolaryngeal and Respiratory Organs, p. 546. 

 VI. The Digestive System, p. 553. 

 VII. Urino-generative Organs, p. 567. 

 VIU. Description of the Plates, p. 573. 



Having in the first part of this Memoir treated of the exterior, of the fleshy body, 

 and of the ligaments knitting the osseous frame of the Sea-lion, it follows that I next 

 take the skeleton into consideration. H. M. Ducrotay de Blainville, in his magnificent 

 ' Atlas of Osteography,' has figured the skeleton of our Otary, and that of the Walrus 

 and the Common Seal ; but neither of the two former is placed in the peculiar and 

 distinctive attitude these animals assume on land. For this reason I have refigured 

 that of the Sea-lion, and added separate illustrations of each of the carpal and tarsal 

 bones — a decided want in his great work. The series of crania figured by me I shall 

 refer to en passant. 



I. The Skeleton and Cranial changes. 

 1. The Skull. 



a. General aspects.— Seen in profile, the skull of the Society's young or nearly 

 adult <? specimen of Otaria jubata exhibits a remarkable flattening of the upper cranial 

 surface ; the base of the cranium from this view also appears pretty level, and is nearly 

 parallel with the horizontal plane of the vertex. From the nasals anteriorly the skull 

 slopes considerably ; and posteriorly the occipital truncation is interrupted by the pro- 

 jecting condyle. In old age, as subsequently to be shown, the skull of this species does 

 not retain the above-mentioned features ; but these evidently hold good in a certain stage 

 of growth. 



Three segments or regions are readily mapped off in this side-view. The first or 

 naso-maxUlary one occupies rather less than a third of the entire length of the cranium, 

 and includes the nasal, the intermaxillary, the maxillary bone, and the teeth as far as 

 the fourth premolar. The anterior or inner margin of the orbit bounds this segment 



VOL. vin. — pakt IX. /«Ke, 1874. ^^ 



