Vol. XIX,' pp. 3-6 January 29, 1906 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



IDENTITY OF THOMOMYS UMBRINUS (RICHARDSON), 



BY VERNON BAILEY. 



In 1829, Richardson described and named Geomys umbrinus 

 from a specimen then in possession of Mr. Lead beater, a London 

 dealer in natural history specimens. The name has since been 

 the cause of much confusion and has been applied to or placed 

 in synonomy under various species of Thomomi/s or else rejected 

 as undeterminable. This state of confusion has resulted from 

 lack of a definite type locality. Richardson's statement that 

 the specimen "came from Cadadaguois, a town in the south- 

 western part of Louisiana," is evidently an error, as the only 

 use of such name in that region was for the Cadadaguois Indian 

 settlements on the Red River in northeastern Texas. This 

 place, however, is several hundred miles from the range of any 

 species of Thomomys. Hence, if the name umbrinus is ever fixed 

 it nuist be by identification of a known species with the original 

 Leadbeater specimen, now in the British Museum. In March, 

 1905, Dr. Merriam sent to Mr. Gerrit S. Miller, Jr., then in 

 London, specimens of Thomomys fulvus, fossor, and lachnguilla, 

 the three species nearest in range to the region that in 1829 was 

 comprised in southwestern Louisiana, for comparison with the 

 type specimen of umbrinus. Mr. Miller found that none of these 

 agreed in either cranial or external characters with the type, 

 which he described in detail as follows : 



The type of Thomomys umbrinus is a formerly mounted specimen in the 

 British Museum, No. 55. 12. 24. 205, a male in good condition, and with 

 skull in good condition except for one zygoma, one bulla, and the right 

 half of the occipital region. It is a Thomomys but not the same as any 

 of those sent for comparison. Externally it is most like fulvus, but smaller 

 and with more slender claws, especially in front. Color above about as in 

 fulvus, but slightly darker, underparts entirely different, much as in fossar 

 [pale buffy] but even paler, with almost a sharp line of demarkation along 



2— Proc. Biol. Soc. Wash., Vol. XIX, 1906. (3) 



