16 Mr. Holberton's and Mr. Yarrell's 



folds more or less obliquely angular, and were not inaptly conij)ared, 

 originally, to the rugse of earth-worms, or the rings of the aspera arteria. 

 See Elliotson's Translation of Blumenbach's Physiology, Section 212. 



Mexican Dog, young. Canis familiar is, var. Mexlcanus. 



Length from mouth to anus 13 inches; whole length of intestines 5 

 feet 4 inches ; caecum 2 inches, of the ordinary form. Dentition irre- 

 gular and imperfect ; no apparent cause of death. 



Jerboa. Dipus Sagitta, Gmel. 



When divested of its skin, the form of the head in this animal is 

 peculiar. The upper surface of the cranium is nearly square; the mas- 

 toid processes are unusually large, excavated, and their parietes diapha- 

 nous. They occupy the whole space behind the zygomatic arch on 

 either side, and extend beyond the occipital bones backwards, and even 

 with the surface of each parietal bone upwards. From the anterior 

 portion of the nasal bones to the occipital ridge was 1 inch -f-^.; from the 

 anterior surface of the malar bone to the back of the mastoid process of 

 the same side If*^; the width of the head between the edges of each 

 zygoma l-j^^; behind the zygomatic arches |- of an inch; across the 

 mastoid processes 1 inch ; mastoid cells projecting backwards beyond the 

 occipital surface J of an inch. 



The meatus auditorius directed backwards; the malar bones so deep 

 in front that vision is confined to the lateral and backward directions. 

 The masseter muscle, large, arising from the under edge of the zygoma and 

 orbit, passes downwards and backwards to be inserted into the base, angle, 

 and ascending plate of the inferior maxilla ; raising, bringing forwards, 

 and also giving a limited degree of lateral motion to the lower jaw. The 

 muscle analogous to the temporal arising from the fossa in front of the 

 orbit, passing under the zygoma, is inserted on the fore part and side 

 of the lower jaw. The portio dura passed outside the muscle elevating 

 the jaw, under the edge of the zygoma to the angle of the mouth to be 

 distributed over both lips. The branches of the infra-orbital nerve were 

 distributed in the usual nianner. The reason for noticing these nerves 

 was on account of their unusually large size. 



