328 



BULLETTISr 56, UNITED STATES NATIONAL MUSEUM, 



Fig. 51.— ClTELLUS TRIDECEMLIXEATIS. FoRT SNELI^ 

 ING, MlNNESOT.\. (CAT. No. 37212, I'.S.N.M.) 



Length, 2i><> nun.; tail, 108; hind foot, 4<>. The grouiul color of the 

 upper .surface is clove brown, fading with wear to prouts l)rown; on 

 this there are a])Out eight continuous lines of brownish white, alter- 

 nating with about seven rows of 

 light spots. Under surfaces, 

 including feet and iinier aspect 

 of limbs, clay color. Tail slen- 

 der, subterete, with the hairs 

 t)rown at base, banded with 

 black, and tipped with yellow- 

 ish. 



Cranial and dental charae- 

 ti't's. — The skull bears a greater 

 resemblance to that of Tain las 

 striattis than do those of the 

 other species of the genus, notwithstanding the presence of two 

 upper premolar teeth, the first of which is functionall}^ developed 

 and rather large. Skull elongated, tapering anteriorly, with small 

 audital l)ulhe, and a long, narrow interpterygoid space. The lateral 

 teeth are not set so obliquely as in Citellus terctlcaudas. Figs. 50 and 51 

 show the skull of typical Citellus tridecemlineatvs. 



ICTIDOMOIDES, new subgenus. 



Tiipe. — [>SV/'itr«s] mexicanuH Krxleben, Syst. Regni Anini., I, 1777, p. 428 

 { = Citellus viexicanus). 



Characters. — Intermediate between Ictldomyx 'And XerosperiiiopJt 11 us., 

 with tail resembling OtospermojjMliis. Braincase broader than in 

 letldomt/s^ its breadth, measured at roots of zygomata below, greater 

 than the distance from posterior border of occipital condyle to molar 

 teeth; skull higher in frontal region, with rostrum more depressed, 

 and nasals relatively longer, the internasal suture measuring consider- 

 abl}' more than the distance from front premaxilla to anterior pre- 

 molar; audital bulh\3 larger. Compared with Xerosperinophllus these 

 differences are exactly reversed. Color pattern likewise intei'mediate. 

 Tail three-fourths the length pf head and bodv, somewhat flattened, 

 and bushy. 



CITELLUS MEXICANUS PARVIDENS (Mearns). 

 RIO GRANDE GROUHD-SaiTIRREL; SMALL-TOOTHED GROtTND SaUIRREL. 



SpermopMlus mexicanus parvidens Mearks, Proc. U. 8. Nat. Mus.,XA^III, p. 443, 

 May 23, 1896 (advance sheet published March 25, 1896; original descrip- 

 tion). — Miller and Rehn, Proc. Bost. Soc. Nat. Hist., XXX, No. 1, Dec. 27, 

 1901, p. 52 (Syst. Results Study N. Am. Mam. to close of 1900). 



SpermophiJus mexicanus, Baird, Mam. N. Am., 1857, p. 319; U. S. and Mex. 

 Bound. Surv., II, Pt. 2, Mam., 1859, p. 39.— Allen, Proc. Bost. Soc. Nat. 

 Hist., XVI, 1874, p. 291 (in part) ; Monogr. N. Am. Rodentia, 1877, p. 868 

 (i« part); Bull. Am. N. Am. Mus. Nat. Hist., Ill, No. 2, 1891, p. 223 (Texas 

 and Tamaulipas); YI, 1894, p. 182 (Texas). 



