DICROSTONYX 151 



[of ' Myodes torquatus '] on the island of Arikamtcluclii, in 

 Behring's Straits, near the Asiatic shore." 



3. Dicrostonyx rubricatus Richardson. 

 (Synonymy under subspecies.) 



Range. — Arctic America from the Alaskan Peninsula eastwards 

 along the Arctic coast to the western shores of Hudson's Bay. 

 Represented by a subspecies upon the island of Unalaska ; and 

 probably inhabiting the more westerly islands of the Arctic 

 Archipelago. 



Characters. — Essential characters closely resembling those of 

 D. torquatus, of which D. rubricatus is clearly the New World 

 representative. Characters, if any, differentiating the skull from 

 that of D. torquatus not at present satisfactorily known. Cheek- 

 teeth of the more complex type ; m^ and m^ usually with well- 

 developed postero-internal vestigial angles, the hind walls of 

 their postero-internal triangles always retaining their thick 

 enamel and concave form ; 711^ usually with a pair of anterior 

 vestigial angles. Outward appearance, in summer, variable 

 with the subspecies ; the typical form from Alaska making rather 

 a near approach in coloration to D. torquatus, while the western 

 subspecies has a peculiarly uniform reddish-grey pelage with a 

 sharply defined black spinal stripe extending from the head to 

 the root of the tail. 



Remarks. — D. rubricatus is undoubtedly very closely related to 

 the Old World D. torquatus, and until more material representing 

 the latter is available, the status of D. rubricatus wiU remain doubt- 

 ful. Three well-marked subspecies are currently recognized, two 

 inhabiting the mainland of N. America and a third confined to 

 the island of Unalaska. 



3a. Dicrostonyx rubricatus rubricatus Richardson. 



1839. Arvicola rubricatus Richardson, Zool. Capt. Beechey's Voyage, 

 1839, p. 7. 



1845. HypudiBus rubricatus Schinz, Synopsis Mamm., 2, p. 250. 



1877. Cuniculus torquatus Coues, Monogr. N. Amer. Rodentia, Muridae, 

 p. 246 (part). Not of Pallas. 



1896. IHcrostony.v torquatus Miller, N. Amer. Fauna, No. 12, p. 38 

 (part). 



1900. Dicrostonyx nelsoni Merriam, Proc. Washington Acad. Sol., 2, 

 p. 25; MUlcr, " List," 1912, p. 207.1 



1900. Dicrostonyx hmlsonius alascensis Stone, Proc. Acad. Sci. Phila- 

 delphia, 1900, p. 37 ; Miller, " List," 1912, p. 207. 



i- —^ ■ • 



' TlirouL;h((ut this work these abbreviations are used for : — 



1. AhLi.ER, List of North American Land Mammals in the United 



■States National Museum, 1911. ISmithsonian Inst. U.S. Nat. 

 Mus. Bull., 79, 1912, pp. 1-455. 



2. Mn^LEE, List of North American Recent Mammals. Smithsonian 



Inst. U.S. Nat. Mus. Bull., 128, 1924, pp. 1-673. 



