328 



BULLETIN 56, UNITED STATES NATIONAL MtTSHUM. 



Length, 290 mm.; tail, 103; hind foot, iO. The ground color of the 

 upper surface is clove brown, fading with wear to prouts brown; on 

 this there are about eight continuous lines of brownish white, alter- 

 nating with about seven rows of 

 light spots. Under surfaces, 

 including feet and inner aspect 

 of limbs, clay color. Tail slen- 

 der, subterete, with the hairs 

 brown at base, banded with 

 black, and tipped with yellow- 

 ish. 



Cranial and dental cha/rac- 



ters. — The skull bears a greater 



_ „ „ „ „ resemblance to that of Tam.ias 



Fig. 51.— ClTELLTJSTBIDEOEMLINEATUS. POKT SNELI^ x^^^ 



ING, Minnesota. (Cat. No. 37212, U.S.N.M.) striatuS than do thosC of the 



other species of the genus, notwithstanding the presence of two 

 upper premolar teeth, the first of which is functionally developed 

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

 audital bullae, and a long, narrow interpterygoid space. The lateral 

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

 show the skull of typical Citellus tridecemlineatus. 



ICTIDOMOIDES, new subgenus. 



Type. — [Sciurus] mexicanus Erxleben, Syst. Eegni Anim., I, 1777, p. 428 

 ( = Citellus mexicanus ) . 



Characters. — Intermediate between Ictidomys 2iaA Xerospermophilus, 

 with tail resembling OtospermopMlus. Braincase broader than in 

 Ictidomys., 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- 

 ably more than the distance from front premaxilla to anterior pre- 

 molar; audital bullae larger. Compared with Xerospermophilus these 

 differences are exactly reversed. Color pattern likewise intermediate. 

 Tail three-fourths the length of head and body, somewhat flattened, 

 and bushy. 



CITELLUS MEXICANUS PARVIDENS (Mearns). 

 RIO GRANDE GROTJND-SaUIRREI; SMALL-TOOTHED GROimD-SQTTIIlREL. 



Spermophilus mexicanus parvidens Mearns, Proc. U. S. Nat. Mus., XYIII, p. 443, 

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

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

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



Spermophilus 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. Naf 

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

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

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



