RODENTIA ARVICOLINA MYODES. 555 



an inch long, and reaching to the base of the second claw. The third nail is longest ; the fourth 

 is a little shorter ; the second reaches beyond the base of the third. 



The hind feet are short and broad. The soles are densely hairy, except under the toes ; the 

 tubercles are naked, however. The three central toes are longest and nearly equal ; the first 

 claw extends nearly to the base of the second ; the fifth beyond the base of the fourth ; the first 

 claw again reaches as far as the middle of the fifth. The longest toe, with claw, is about one- 

 third the whole foot ; without the claw, about one-sixth. The claws are long, curved, and 

 compressed, channelled beneath ; more curved than the anterior, which likewise are much 

 channelled and blunted. All have stiff bristles covering their bases. 



The tail is very short, shorter than the hind feet ; densely coated with hair. 



My odes thus differ from Arvicola in the much broader head, shorter tail, much more fossoried 

 fore feet, with very long claws ; a long compressed strap-shaped nail to the thumb. The sole 

 of the hind feet with hair to the roots of the toes. 



The skull of this species is very massive and broad, measuring 1.30 by .8V, or as 100 to 67 

 nearly. The muzzle is long in proportion, projecting beyond the zygoma between one-third 

 and one-fourth the total length. It slopes very rapidly downwards in nearly a straight line ; 

 viewed from above, the nasal bones and nasal branches of the intermaxillaries are of equal 

 length, and reach a little behind the anterior outline of the anterior root of the zygomatic arch, 

 not to its posterior. The orbits proper are very large ; the temporal fossae small ; the outline 

 of the cranium proper nearly square. The interorbital region is much contracted, considerably 

 narrower than the muzzle ; there is an acute central crest, which bifurcates at the end of this 

 region, and, passing backwards in a sigmoid curve to the nearly plane and vertical occiput, 

 encloses a plane space on the top of the head. The interparietal bone occupies the posterior 

 part of this plane ; it is quadrangular, a little wider than long. The zygomatic arch is 

 emarginated anteriorly at its base ; its lateral outline is very high. 



The bony palate ends behind in a shelf, projecting a little over the cavity of the internal 

 vases ; the structure here is intermediate between that of Arvicola and Hypudaeus. Thus, there 

 is a fossa on each side against the inner side of the posterior molar, but these, in a measure, are 

 pushed under the posterior extremity of the palatine arch. This posterior outline is broadly 

 emarginated. 



The line of molars is rather short, about one-fourth the total length ; it is situated far back, 

 the centre of the axis falling about opposite the middle of this line, or a very little anterior to 

 it. The distance between the molars and incisors is more than one-third the total length. The 

 lines of molars converge anteriorly, their inner outlines meeting at the incisors. 



The incisors are thick and large ; very much rounded anteriorly. The upper are bevelled on 

 the exterior so much that no dentine is visible laterally. In fact, the tooth is an enamel tube, 

 nearly meeting on the posterior side, their lower or terminal half, with half the tube cut away 

 behind, and enclosing very little dentine. l 



The anterior molars of both jaws are longest ; the others, successively, a little shorter. The 

 lateral indentations of the enamel or re-entrant angles are very deep, extending almost entirely 

 across the teeth ; very conspicuously different in this respect from Arvicola, the triangle, also, 

 being generally very narrow and elongated. The first upper molar is composed of five 

 triangles, one anterior and two on each side ; the first lateral being internal, the last external. 



' The root of the lower incisor ends on the inside of ihe line of molars opposite the middle of the posterior molar, instead of 

 passing under the posterior molar, and extending to the posterior edge of the condyloid process. 



