328 



BULLETIN 56. UNITED STATES NATIONAL MUSEUM. 



Fig. 51.— Citellus tridecemlineatus. Fokt Snell 

 [ng, Minnesota. (Cat. No. 37212, i.s.n.m.i 



Length, 290 mm.; tail, L03; hind foot, 40. 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- 



nat ing 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 <ui<l <l<nt<il <-/hii'<ic- 

 t, rs. The skull bears a greater 

 resemblance to that of Tamim 

 striates than do those 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 ( 'itellus t<n ticaudus. Figs. 50 and 51 

 show the skull of typical Oitellus tridecemlineatus. 



ICTIDOMOIDES, new subgenus. 



Type. — [Sciurus'] mexicanus Erxleben, Syst. Rejini Anim., 1, 1777, p. 428 

 {•=dtellus mexicanus). 



( 'haracters. Intermediate between Ictidomys and X^erosperm op Mlus, 

 with tail resembling OtospennopMlus. Braincase broader than in 

 Icbidornys, its breadth, measured at roots of zygomata below, greater 

 than tin 1 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 Xerospermophihts 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 GROUND SQ.UIRREL; SMALL-TOOTHED GROUND SQUIRREL. 



Spermophilus mexicanus parvidens Mearns, Proc. P. S. Nat. Mus., XVIII, p. 44.">, 

 .May 2:;, L896 (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 Stufly N. Am. Mam. to close of 1900). 



SpermophUus mexicanus, Baled, Mam. X. Am., 1857, p. 319; V. S. and Mex. 

 Bound. Surv., II, I't. 2, Mam., 1859, p. 39.— Allen, Proc. Post. Soc. Nat. 

 Hist., XVI, IS74, p. 201 (in part); Monogr. X. Am. Rodentia, 1S77, p. 8(58 

 (in part); Bull. Am. X. Am. Mus. Nat. Hist., Ill, X... 2, L891, p. 223 (Texas 

 andTamaulipas); VI, L894, p. 1S2 (Texas). 



