820 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 



is ;i heterogeneous group, embracing quite diverse species, some of which 

 strongly approach Sciviits, while others foreshadow Cynotnys, and others 

 still grade byalraosl insensible stages into Tamias. The group was first dis- 

 membered* by Brand! in 1844, who divided il into two "subgenera", namely, 

 Colobotis (also written later in the same paper " Otocolobus") and Otospermo- 

 philus. To the firsl he referred all Ihe Old World species known to him, and 

 also three of ihe North American species; the latter is exclusively American. 

 These two groups are based on slight peculiarities of dentition (particularly 

 in respect to the size and form of the first upper premolar), the size of the 

 ear, and the length of the tail. The Old World species of Colobotis are all 

 short-tailed, with small or rudimentary ears, the tail with the hairs exceeding 

 a length ot two inches in only one species (S. eversmaimi), being generally 

 considerably less than one-fourth of the length of the head and body. Oidy 

 one (S. richardsoni) of the three American species referred by Brandt to this 

 group really belongs here, the others (S. "hoodi" — tridecemlineatvs, and S. 

 franklini) having few characters in common with the others. Otospermophi- 

 lus is a much more natural division, but. was made to include S. mexicanus, 

 which, as will be shown later, belongs to a wholly different division. The 

 other species referred to Otospcrmophilus were S. grammurus (with its varie- 

 ties and synonyms) and S. lateralis; the affinities of the last named are 

 divided between this group and Tamias, with a preponderance toward the 

 latter. Brandt divided the Old World representatives of Colobotis into three 

 sections ("A", "B", and "C"), based wholly on the seasonal and valueless 

 character of the pilosity of the soles, which he appears to have supposed to 

 be a constant character in adults. His section "B" (consisting of S. cvers- 

 inaiuii and S. parry I) he says resembles Otospermophilus in the length and 

 structure of the tail. This is also true of other characters; it hence forms 

 a natural and well-marked subdivision of his subgenus Colobotis. 



In 1855, Brandt's divisions and subdivisions were adopted by Giebel. 

 Baird, in 1857, while pointing out the worthlessness of any distinctions based 

 on the pilosity of the soles, thought Brandt's subgenus Otospermophilus enti- 

 tled to permanent recognition, and adopted it with merely the removal there- 

 from of S. mexicanus to Colobotis, under which latter group Professor Baird 



* Lichtenstein, however, about 1H30, proposed the name CiUlhts for certain species, but without 

 giving for the group any tangible diagnosis. The first species described under this name was S. mexi- 

 caniix, tint lie also described two Old World species (C.fulvus and C. miigosaricux) that differ widely from 

 8. mexicanus, belonging in fact to an entirely different section of the genus, lirandt makes, and quite 

 properly, as it seems to me, Citillus merely a synonym of Spermojpl'ilus. 



