240 



PROCEEDINGS OF THE ACADEMY OF 



[1894. 



loops (with the addition in rare cases of a narrow antero-external 

 h)op), never S-shaped (fig. 5); m ' and - witli middle loop un- 

 divided (reaching completely across tooth); molar series relatively 

 short ; condylar ramus low and directed obliquely backward ; coro- 

 noid notch horizontal or nearly so [nearly vertical in Xcnomys and 

 Hodo))iijs] ; angle of mandible only moderately inflected ; sym])hysis 

 relatively short and sloping strongly forward. 



The accompanying illustration (fig. 5) shows the two extremes 

 in pattern of m ' , and differences in the crowns of the other molars 

 also. The dominant type of m ' throughout the genus is similar 

 to that of N. tenuicauda (fig. 5, c), a member of the mexicana series. 



Fig. 5. a and r. Upper molar rrowiis. A and d. Lower molar crowns. 



a. h. NeoLoma deserloruni Merriani. Death Valley, t'alif., No. 34138. c?. 

 (xf). ) c. d. Neoloma tenuicauda Merriam. Sierra Nevada, Jalisco, Mexico. 

 45629 ?. Type, {x 5). 



Neotoma is not in any sense a highly specialized type, but it is a 

 very compact genus, its most divergent branches hardly meriting 

 subgeneric recognition. Some of its members point strongly toward 

 derivation from Hi)d(>iaij><, as may be seen in the iVecfo;/(//.s-like au- 

 dital bulhe and other cranial characters of Neoioma pennt^ylvanlca, 

 and in the high, upturned condyle of the ?uex-icau« group, but the 

 inmiediate antecedent forms leading up to Neotoma from lL)doniij.'<, 

 or some similar type, are not known. The oldest forms of which we 

 have any knowledge, those from the cave deposits of Missouri, Ken- 

 tucky, Virginia, and Pennsylvania, are fully modernized species of 

 NeofoiiKi ])roj)er. 



Of the living species, N. pennaylvanica may be regarded as the 

 most primitive, since it po.ssesses several characters, not shared by 

 the others, that jioint back to Hodoru.i/s. Moreover, poDisylviinlca is 

 more nearly intermediate between the two subgenera — Neotoma 

 proper and Teoiioma — than any other known species, indicating that 



