96 



NORTH AMEEICAN FAUNA. 



[NO. 39. 



Distribution. — Coastal Plain of southern Sinaloa and Tepic, from 

 Mazatlan south to Colomo (fig. 9). 



Characters. — Size medium, hind foot 30 mm.; pelage thin and 

 harsh; color dark brown or blackish; skull short and wide, with pro- 

 jecting incisors; ears small; claws slender; mammae in 3 pairs. 



Color. — Dark umber, brown, or brownish black; underparts brown- 

 ish or plumbeous; ears, feet, and tail nearly naked, but lower part of 

 feet and tip of tail usually white when there is hair enough to show 

 color. 



SJcull. — Slightly heavier and longer than in umbrinus, but of the 

 same general characters, with short nasals and less-projecting incisors; 

 base of zygoma slightly indented and the greater part of lachrymal 

 adnate to it; posterior tips of prem axillae narrowed and extending 

 slightly back of truncate tip of nasals; pterygoids wide apart. 

 Dentition slightly heavier than in umbrinus; incisors dark orange and 

 very lightly grooved. 



Measurements. — Average of 3 females from Rosario: Total length, 

 196; tail vertebrae, 68; hind foot, 29. Adult male from Mazatlan: 

 208, 66, 31. Slcull (of adult male from Mazatlan): Basal length, 36; 

 nasals, 13; zygomatic breadth, 25; mastoid breadth, 20; alveolar 

 length of upper molar series, 8. 



Remarlcs. — TJiomomys atrovarius is a well-marked, thin-haired, 

 nearly concolor, tropical species in which the skull characters show 

 close afiuiities with the umbrinus group. 



Specimens examined. — Total number, 14, as follows: 



Sinaloa: Mazatlan, 2; Plomosas, 2; Rosario, 5; Tatemales, 1. 

 Tepic: Colomo, 1; Navarete, 2; Pedro Pablo, 1. 



Thomomys talpoides Group. 



THOMOMYS TALPOIDES TALPOIDES (Richardson). 



Saskatchewan Pocket Gopher. 



Cricetus talpoides Richardson, Zool. Journ., Ill, 518, 1828. 

 Geomys talpoides Richardson, Fauna Boreali-Americana, 204, 1829. 

 S[accophorus] talpoides Fischer, Synopsis Mammalium, 588 ("388"), 1830. Taken 

 from Richardson. 



Geomys horealis Richardson,^ Sixth Ann. Rept. Brit. Assn. for 1836, V, 150, 156, 

 1837. Renaming of talpoides. 



1 Geomys horealis of Richardson has been generally considered a nomen nudum and the name dated 

 from Bachman, two years later, based on a different species. Richardson first used the name (loc. cit., 

 150) as " Geomys borealis, Rich. nov. sp." On page 156 he states that " Geomys horealis iahabits the Plains 

 of the Saskatchewan," and on page 157 he gives good descriptive characters in comparison with several 

 other species. He says ''horealis and talpoides have a very fine groove close to the inner margin of each 

 upper incisor," but evidently failed to detect the much finer grooves on the incisors of bulbivorus and 

 umbrinus with which he was making the comparison. As Dr. Allen has pointed out (Bui. Am. Mus. 

 Nat. Hist., V, 61, 1893) Richardson was evidently renaming his talpoides, of which he here (p. 156) very 

 strangely changes the habitat to Florida. It therefore seems necessary to consider horealis a synonym 

 of talpoides. Bachman's horealis (1839), of which the type is extant and perfectly identifiable, is the same 

 as clusius of Coues (1875). 



Since writing the foregoing I have received a letter (Mar. 15, 1915) from Mr. OMfield Thomas, of the 

 British Museum, expressing his opinion that horealis of Richardson is not a nomen nudum. 



