1866.] ON THE ANATOMY OF THE CRESTED AGOUTI. 383 



9. On the Anatomy of the Crested Agouti [Dasyprocta cris- 

 tata, Desm.). By St. George Mivart, F.Z.S., Lecturer 

 on Comparative Anatomy at St. Mary's Hospital, and 

 James Murie, M.D., Prosector to the Zoological Society. 



The animal, the dissection of which forms the subject of the pre- 

 sent communication, died lately in the Society's Gardens. It had 

 lived above four years in the collection, having been originally pre- 

 sented to the Society by Captain M. D. Stewart in October 1861. 



External Characters. 



With reference to general appearance, our specimen corresponded 

 to Mr. Waterhouse's* description of the variety of Dasyprocta 

 cristata — the crest of the head being black, the loins and hinder 

 portions of the body bright rust-colour, the hairs of the latter parts 

 very slightly annulated with black. 



Professor Rymer Jonesf says that there are in the Agouti as many 

 as from twelve to fourteen nipples ; and Mr. Waterhouse X notes that, 

 according to Desmarest, there are in D. cristata six mammae, whilst 

 D. aguti has twelve ; but he himself found eight teats both in D. 

 punctata and in D. acoucky. The specimen brought under our con- 

 sideration confirms Mr. Waterhouse's observations, possessing as it 

 does four pairs of teats, the foremost (as in I), punctata) being axil- 

 lary, while the hindmost are situated in the inguinal region. 



It may be interesting to note some of the outward differences ex- 

 hibited by the feet of Dasyprocta cristata as compared with those 

 of Cavia aperia and Lepus timidus, corresponding as they do to 

 some extent with the distribution of the muscles and tendons. 



In the first-named species the back of the fore foot is sparsely 

 clothed with hair, which on the inner side is shorter, finer, and 

 lighter in colour. The nails are nearly straight, solid, and broader 

 than in the Hare. The sole, which is bare, has three pads (see 

 fig. 1, A) — a large semilunar one posteriorly, a small roundish one 

 at the base of the index, and another larger irregularly oval-shaped 

 and slightly divided one (also proximally situated) between the third 

 and fourth digits. There are likewise numerous wrinkles, running 

 in the main transversely, producing on the toes somewhat the ap- 

 pearance of scales. The pollex is a mere tubercle hidden by a por- 

 tion of the posterior pad, so that externally four toes only are to be 

 observed. 



The foot of the Guinea-pig, besides its smaller size, differs from 

 that of D. cristata in the less wrinkled condition of the sole, in hav- 

 ing four distinct pads, the anterior one being the largest, and in all 

 of these having a thicker cushion of fat (fig. 1, B). 



* Nat. Hist, Mamm. vol. ii. pp. 384, 385. 



t Cyclopaedia of Anatomy and Physiology (1852), vol. iv. p. 396. 



+ Loc. cit. p. 384 (footnote) and p. 393 (text). 



