178 



a rounded figure, and when pressed down did not completely cover 

 the rima of the glottis until the larynx was depressed towards its 

 base. 



"A distinct fold or duplicature surrounded the opening of the 

 nares into the asophagus ; which tube was small, and had its lining 

 membrane corrugated into longitudinal folds. 



" The sublingual glands were large. 



" The trachea was about 3 inches in length to its bifurcation, and 

 4- an inch in diameter ; the bronchi were about 1 inch long before 

 entering the lungs. 



" To the q,bove sketch of the visceral anatomy of the Coypus, I have 

 to subjoin a few observations on some portions of its skeleton. 



" Of the skulls of such Rodentia as I have been enabled to com- 

 pare with that of the present animal, although it agrees in many 

 points with that of Capromys, the one which approximates the 

 nearest to it is that of the Capybara. The main outline and con- 

 tour of both are very similar ; they both agree in the flatness of their 

 upper surface, in the elongation of their form, in the magnitude of 

 the suborbital foramen, and in the development of the processes of 

 the occipital bone continued from its transverse crest. When, how- 

 ever, we descend to details, numerous and striking points of diiFer- 

 ence are immediately observable. In the Capybara, for instance, the 

 margin of the orbit is circular or nearly so, and the zygomatic arch, 

 broad and strong, has its lower edge brought down considerably be- 

 low the level of the molares : whereas in the Coypus the margin of the 

 orbit approaches to a square, and the zygomatic arch is narrow and 

 scarcely depends to a level with the crown of the molares, though it ad- 

 vances much further than either in the Beaver or Water Rat; in which 

 animals the orbits, of an oval shape, have a less lateral and more 

 vertical aspect. In the Coypus the temporal fossa are deeper than 

 in the Capybara or the Beaver, and the external auditory foramen 

 runs obliquely forwards and downwards, while in the Capybara it 

 runs obliquely downwards and inwards, and in the Beaver down- 

 wards and backwards. The frontal bone is divided by a permanent 

 longitudinal suture, as it is also in Capromys ; whereas in the Capy- 

 bara, the Water Rat, and the Beaver no trace, at least in adults, of 

 such a separation is visible. The Beaver when semiadult exhibits, 

 however, a slight appearance of it. 



" The general admeasurements of the skull of the Coypus before 

 me are as follows : 



In. Lin. 



From the end of the nasal bones to the occipital ridge. . 4 6 



From the lower edge of one zygoma to the opposite . . 2 9 



Breadth of the frontal bones between the orbits 1 3 



From the outer edge of the last molar tooth to the edge 



of the zygoma . 5 



From the base of the incisors to the base of the first molar 1 3 

 From the crovra of the first molar to the top of the skull 

 where the nasal and frontal bones unite in a straight 



line 1 9 



