1894. NATURAL SCIENCES OF PHILADELPHIA. 225 



A NEW SUBFAMILY OF MURINE RODENTS— THE NEOTOMINiE— WITH 



DESCRIPTION OF A NEW GENUS AND SPECIES AND A SYNOPSIS 



OF THE KNOWN FORMS. 



BY DR. C. HART MERRIAM. 



A study of the rich collections of American Murine Rodents 

 brought together by the V. S. De])artment of Agriculture, shows 

 that the genus NeoUxma is one of a group of closely allied forms 

 which differ so radically from the tuberculate crowned Murines, with 

 which they have been commonly associated, that the propriety of 

 separating them as an independent subfamily seems evident. 



The unparalleled series of Mexican Rodents collected by Mr. E. 

 W. Nelson in connection with his work for the Division of Ornith- 

 ology and ^lammalogy of the U. 8. Department of Agriculture, 

 contains a large number of wood rats, several of which are not 

 properly referable to the genus Neotoma. Two of these were de- 

 scribed by me sometime ago, under the names Xenomys nelson i and 

 Neotoma alleni,^ the former being made the type of a new genus. 

 In the original account of Neotoma alleni attention was called to the 

 circumstance that the crown of the last lower molar is shaped like 

 the letter »S, instead of exhibiting two transverse loojis as usual in 

 the genus Neotoma, and it was remarked that this peculiarity might 

 prove worthy of subgeneric recognition (p. 1G7). In the course of 

 a subsequent study of the American wood rats, it was discovered that 

 the character in question, which is one of great value, is correlated 

 with a number of important cranial characters, making it obviously 

 undesirable to retain the animal longer in the genus Neotoma. 

 Anieghino has described and figured two related rodents from the 

 I'ampean Pliocene deposits near Villa de Lujan, in the province 

 of Buenos Ayres, which he has named Ptyssoplwnis elegana' and 

 Tretomyii atavn>i.^ His description of the former is based on the 

 broken ramus of the mandible of an apparently immatui-e indi- 



' Proc. Biological Soc. of Wasliiiigtou, VII, Sept. 1892, 150-lf)3 : lOT-KW. 



■^ ManiniifVros Fosiles do la licpiihlica Argeiitiua, por Floivntino Amcghino 

 iSHi), 111, 112, and pi. iv, figs. 1, 1^-. 



' llii.l.. Hit, 120, and pi. iv, fig. 16. 

 IG 



