332 ON A QUADRUPED. 



ORDER RODENTIA. 

 Genus* ISODON. 



ARTIFICIAL CHARACTER. 



Clavicles perfect ; molares sixteen, prismatic, not 

 divided into radicles ; toes divided. 



NATURAL CHARACTER. 



Clavicles robust, perfect ; incisores not narrowed 

 at tip, but very obtusely rounded ; their transverse 

 section preseuts a triangular figure, of which the an- 

 gles are rounded ; molares sixteen, the two series in 

 each jaw converge a little towards the front, and con- 

 sist of four teeth in each series, prismatic, not divided 

 at base into radicles ; their crowns flat, and traversed 

 equally from the base to the summit by lamina, which 

 on the summit and base of the tooth terminate pre- 

 cisely alike, in zigzag lines, and are the effect of 

 the sides of the tooth being folded deeply inwards 

 transversely and with but little obliquity : the inner 

 angles of the folds attain or surpass the centre of the 

 width of the grinding disk, and do not oppose, but 

 pass between the angles of the opposite folds ; each 

 molar of the superior jaw has two folds on the exte- 

 rior and one on the interior side, and of the inferior 

 jaw there are two folds on the interior side and only 

 one on the exterior ; the interstices are filled near the 

 summit with a cortical substance, but at the base they 

 are void 5 the form of the grinding surface of the mo- 



