73 



The nrytenoid cartilages present the same peculiarity as in the above- 

 named animal, being continuous with each other at their ff/jice*. This 

 adhesion does not of course prevent their being drawn apart at their 

 bases where the chordce vocales are attached 5 the crko- and thyreo- 

 arijtcnoidei being strongly developed for that purpose. The chordce 

 vocales are distinct shining ligamentous threads j the crko-tlujroidei, 

 which render these chords tense, were largely developed, covering the 

 whole of the anterior space between the two cartilages to which 

 they are attached. They are no doubt materially concerned in pro- 

 ducing the sharp cry of this animal. The saccuU laryngis are narrow 

 but deep. The epiglottis is broad and of a rounded form ; it has a 

 linear depression at its base, and a longitudinal ridge along the middle 

 of its posterior or laryngeal surface, which fits into the rima glottidis 

 when the cartilage is depressed. The margin of the soft palate was 

 in close contact with the tongue anterior to the epiglottis, which, to- 

 gether with the apices of the arytenoid cartilages, rose into the pos- 

 terior nares ; the structure, indeed, seemed to forbid the epiglottis 

 passing under the soft palate, although we must suppose it to do so 

 when the shrill cry is produced ; but the grunting noise appears to be 

 emitted by the nose. 



" The tongue corresponds in form to the space between the two 

 rows of inferior molares ; is compressed laterally, and deeper than it is 

 broad. It grows gradually narrower to the apex-, which is neatly rounded 

 and is impressed with small follicular apertures. Half an inch of the 

 extremity only is free. The papillce on the surface are extremely mi- 

 nute ; towards the dorsum they are conical and retroverted, and nu- 

 merous delicate lines converge towards the root of the tongue. Like 

 the Acot(c.hy, it wants the elevated or super-imposed portion observ- 

 able in the Beaver and Guinea-pig. 



" T\\^i parieies oi the pharynx are extremely thick; the islJimus 

 fauciiim is long, narrow, and conical, diminishing backwards, as in the 

 Beaver; the sides are not produced into folds, but the whole of this 

 structure is evidently adapted to the same end, as was first pointed out 

 by Mr. Morgan in the structure of ihefaiicesoi the Copybara. The 

 inner membrane of the cesophagus is disposed in longitudinal rngce. 



" The eye is stated by M. Desmarest to be moderately large, but the 

 largest diameter of the globe does not exceed .5 lines j the apparent 

 magnitude is owing to the great proportion in the cornea, the diameter 

 of its base being only one line less than that of the globe itself. This 

 large size of the cornea is found in most of the Rodentia, especially 

 in those whose habits are nocturnal. It prevails also in the Lemii- 

 ridcp- and is evidently for the purpose of admitting as much light as 

 possible into tlie globe. The loss of refractive power is in most of these 

 cases compensated by a greater convexity in the lens; which in Cn- 

 promys is 3 lines in the long and 2 in the short diameter. The 

 conjunctive membrane has a brown stain round the margins of the 

 cornea ; the rest is white and of a firm texture. The sclerotic is so 

 tlun as to be discoloured by the pigmentuni nigrum beneath, so that 

 the anterior half is nearly black ; which, when seen through the white 



