Howell — Six New North American Ground Squirrels. 213 



longer, with more black on distal half; dorsal spotting finer; skull larger, 

 with narrower ros.trum. 



Description of type. — Upperparts wood brown (of Ridgway, 1912), 

 finely speckled, chiefly on hinder back, with white; tail above, light pinkish 

 cinnamon on proximal half, the distal half bordered with fuscous-black, 

 and edged with buffy white; tail beneath, pinkish buff, bordered with 

 fuscous-black and buffy white; underparts white. 



Measurements. — Average of 12 adults from the type locality: Total 

 length, 242.6 (232-253); tail vertebrae, 84.4 (76-92); hind foot, 35.7 

 (34.5-37). Skull. — Average of 10 adults from tjTje locality: Greatest 

 length, 40.1 (38.9-41.1); zygomatic breadth, 23.8 (22.9-24.5); breadth of 

 cranium, 18.6 (18.2-19); interorbital breadth, 8.4 (7.8-8.9); least post- 

 orbital breadth, 14 (12.8-15.1); length of nasals, 13.6 (13-14.5); maxillary 

 tooth row, 7.5 (7.1-8.1). 



Remarks. — Before undertaking further subdivision of this group, it was 

 found necessary to identify the typical form, named without indication of 

 its locality. Fortunately, the original specimens forming the basis of the 

 description of spilosoma are still in the British Museum collection, and 

 with the kind assistance of Mr. Oldfield Thomas, I have been able to 

 obtain direct comparison of certain specimens in the Biological Survey 

 collection with these types. Typical spilosoma is found to range from 

 Durango City southward to Aguas Calientes, whereas the present form 

 occupies the plains of north-central Mexico, from southern Chihuahua 

 (Santa Rosalia) southward to San Luis Potosi and eastward to southern 

 Nuevo Leon (Doctor Arroyo). 



Citellus tridecemlineatus arenicola, subsp. nov. 



Type. — Male adult. No. 87,686, U. S. National Museum (Biological 

 Survey collection); collected April 22, 1897, at Pendennis, Kansas, by 

 J. Alden Loring; original number 3988. 



Subspecific characters. — Similar to Citellus t. tridecemlineatus, but smaller 

 and paler, the dark dorsal stripes snuff brown (instead of sepia); similar 

 also to C. t. texensis, but smaller and much paler. 



Measurements. — Average of 8 adults (4 males, 4 females) from type 

 locality: Total length, 238 (214-295); tail vertebrae, 77.7 (71-83); hind 

 foot, 32.2 (31-34). Skull. — Average of 4 adult males from type locahty: 

 Greatest length, 38.3 (37.3-39); palatal length, 17.7 (17-18.5); zygomatic 

 breadth, 23 (22.2-23.6); breadth of cranium, 17.1 (16.8-17.4); least inter- 

 orbital breadth, 11.5 (10.8-11.8); length of nasals, 13.5 (12.9-13.9); 

 maxillary tooth row, 6.8 (6.5-7). 



Range. — Southwestern Kansas, extreme eastern Colorado, northwestern 

 Texas, western Oklahoma, and eastern New Mexico. Specimens have 

 been examined from the following locahties: 

 Colorado: Eureka Hill, Cheyenne County; Leroy; Monon, Baca County; 



Springfield. 

 Kansas: Oakley; Pendennis. 

 Oklahoma: Woodward. 



