QUADRUPEDS. 191 



grinders. In some, these teeth seem, from the distribution 

 of the enamel, to consist of two or more teeth joined to- 

 gether, as the entire tooth is constructed of transverse and 

 vertical plates of enamel and ivory. In the second, the 

 enamel is distributed more superficially, covering merely 

 the salient and entering angles of the sides, or penetrating 

 but a short way into the body of the summit. 



(A.) Enamel in vertical plates. 



Subsidiary incisors in the upper jaw. This division in- 

 cludes the genus Lepus of LINNAEUS, and is peculiarly dis- 

 tinguished by two small incisors, placed immediately behind 

 the ordinary ones in the upper jaw. The grinders, which 

 are prismatic, are five in number in the lower jaw, and six 

 in the upper, on each side. The inside of the lips and 

 cheeks hairy. There are five-fingers and four toes. The 

 caecum is uncommonly large, with an internal spiral plate. 



73. LEPUS. With a tail. Ears large, hind-legs long, 

 clavicles imperfect, and a suborbitar space, with the bone 

 reticulated. L. timidus. 



74. LAGOMIS. No tail. Ears and hind-legs of mode- 

 rate size. Clavicles nearly perfect. Suborbitar hole simple, 

 Lepus alpinus, PALLAS. 



No subsidiary incisors in the upper jaw. 



(a.) Roots of the grinders with fangs. Grinders four on 

 each side. 



75. ECHIMYS. Body covered with spines. Hystrix 

 chrysurus. 



76. MYOXUS. Body covered with hairs. Mus avella- 

 ) LIN. * 



* It is probable that these two genera should be associated with the Castor 

 and Histrix, in the last division of the genera, with flat-crowned grinders. 



