50 liErjSIOX OF AMEBIC AX MOLES— TRUE. 



beut backward rather than outward. The termination of the triangu- 

 lar coronoid process of the mandible is broadly trnucated. The angular 

 process is large and strongly uncinate. 



TEETH. 



Dental formula: i, f ; c, |; pm, \; m, jj ; total, 44. 



The lirst upper incisor is large and elongate, with a convex anterior 

 and tiat posterior face and broad cutting edges. Tlie second and third 

 incisors and the canine are subequal, terete, unicuspidate teeth. The 

 first premolar is similar, but decidedly smaller. The second and tliird 

 premolars are similar; both teetli (especially the third) show a tendency 

 to develop a jiosterior cusp. 



The fourth premolar is larger than any tooth that precedes it. The 

 crown is eompressed and recurved and has a large lamellar posterior 

 cusp, and a minute internal basal cusp and also usually a rudimentary 

 anterior basal cusp. The molars ?re similar to those of Scalops aquati- 

 cus, the internal basal cusp being compressed and simple and not 

 extending across the posterior external cusp. 



The first lower incisor is shorter than the second (and in iScapanus 

 californicus much smaller). The third incisor is smaller than the second 

 (in SccqjanKs californicus much smaller). The canine and first, second, 

 and third premolars are sube(iual and larger. All these teeth are single- 

 rooted and unicuspidate, except the prenu>lars, which tend to form a 

 posterior basal cusp of cousiderable size. The fourth premolar is larger 

 than the others, with a pronounced ])Osterior basal cusp and a rudi- 

 mentary anterior one. The molars resemble those of >Scal()2)s aquaticus. 



SKELETON. 



The vertebral formula in this genus is as follows: c, 7; d, 14; 1, 5; s, G; 

 ca, 13 (or 14). Total, 45 (or 40). There are seven intervertebral ossicles, 

 of which the anterior one (which is smaller than the rest) is between 

 the penultinuite and last dorsal vertebra", aiul the last between the 

 posterior lumbar and first sacral. 



The sternum consists of 5 segments and a very large manubrium, 

 which is as long as the coml)ined si-gments. The first pair of ribs joins 

 the sternum a little behind the junction of its intermediate ami 

 posterior third. The manubrium is dilated above and moderately 

 grooved, with raised, but only slightly incurved, borders; the keel is 

 not as deej) as in Scalops, its greatest depth being less than one-third 

 its length. 



The clavicles are about two-thirds as long as broad, deejily notched 

 on the inferior border, and not pierced by a toramen. 



The scapula is as in Scdlojhs, but has a prominent tubercle at the 

 distal extremity of the inferior spine. The humerus is a fourth longer 

 than broad. 



The pelvis is extremely narrow, but the bones of the two sides do 



