174 PROCEEDINGS OF THE ACADEMY OP 



Sigmodont Seines. 



Molars with two tubercles in transverse series. Soles normully' 

 hairy. (New World rats and mice.) 



Genus II. NEOTOMA, Say and Ord. 



Syn. 3fu/t, sp , Say and Ord, 1818 ; Desm., 1833. Arvicola, sp., Harlan, 

 1825. Lemmm, sp., Fiscb.,1839. Neotoma, Say and Ord, J. A. N. 

 S. P. iv. 1825, 346, and of authors ; type, N. floridana. Mi/oxus, sp.. 

 Rich., Zool. Journ. ill, 182S, 517 (JS^ cinerea). Teoiioma! J. E. 

 Gray (same type). 



Ohs. Embracing sigmodont rats of North and Middle America, 

 of the largest size, highly murine in general aspect. None so 

 small as the largest of the other N. American species. There are 

 abundant cranial and external generic characters. Only here we 

 find in one species a bushy distichous tail, almost as in Sciurus 

 a circumstance which doubtless caused the reference of the species 

 to 3I1JOXUS ; but other species of the genus do not show this 

 feature. 



Analysis of Species. 



I. Tail scantily hairy (nearly as in Mus). 



a. Tail bicolor, barely or not as long as the body without the head. 



Feet entirely white. Length 9 inches or less ; tail 6 or less. 



PLORIDAXA. 



b. Tail unicolor, blackish, about as long as head and body. Feet 



partly dusky. 



a'. Large ; about the size and general coloration of iV. floridana. 



PUSCIPES. 



b'. Small ; length about 7 inches. Coloration rich, warm rusty- 

 red, with snowy white uuderparts. (Extralimital.) 



FERRUGINEA. 



II. Tail densely hairy (as in Myoxus), bicolor. Size of the first, or larger. 



CINEREA. 



Ohs. In addition to the foregoing, occurs N. magister, a fossil 

 species, known only by its skull. It is a probable progenitor of 

 series I., if not of the whole. N. cinerea obviouslj^ stands apart; 

 the other species still continue more nearly united, though I have 

 not seen exactly intermediate specimens. 



' Naked in Sigmodon, in subgenus Oryzomys, and almost so in two species 

 of subgenus Vesperimus. 



