SC1URID2B— TAMIAS. 781 



small as it is in T. asiaticus, and is sometimes wholly wanting, as in skull No. 

 4239, from Cape Saint Lucas. In T. lateralis, the fust of the two upper 

 premolars is as large as in some of the Spermopkili, the dentition is heavier 

 than in the other Tamice, and in other cranial features this species is about 

 as well referable to the one group as to the other. T. asiaticus has, as already 

 intimated, two upper premolars, but the first is very small and slender. T. 

 striatus has but a single upper premolar, and the muzzle is narrower and more 

 pointed than in either of the other species. 



The coloration of T. lateralis is quite similar in pattern to that of T. 

 striatus and T. asiaticus, namely, an alternation of dark and light longi- 

 tudinal stripes on the dorsal surface. T. harrisi, however, has only the white 

 stripes. In respect to pattern of coloration, we have the following transition 

 from T. harrisi to T. asiaticus: — T. harrisi has simply a single longitudinal 

 white stripe on each side of the median line of the back ; T. lateralis has 

 the same stripes in the same position, but they are bordered on each side by 

 a stripe of black, that on the outer side being usually much the broader; 

 T. striatus has the two white stripes, bordered on each side by a broad line 

 of black, the outer of which is the wider, with, in addition, a narrow median 

 line of black. There are thus five black stripes and two white ones, the 

 spaces between the inner black lines being gray. In T. asiaticus, these spaces 

 are white or whitish, thus making in this species four white stripes, instead 

 of two, which alternate with black ones of about the same width. The 

 number of stripes thus increases from simply two white ones in T. harrisi 

 to four white ones and five black ones in T. asiaticus. None of the true 

 Spermopkili are thus marked, although some have interrupted lines of white, 

 as 8. tridecemlineatus and S. mexicanus. In all the species of Tamias, the 

 general color of the dorsal surface is gray, with the sides and sometimes the 

 rump washed with rufous. 



In both T. harrisi and T. lateralis, the tail is much shorter than in the 

 other forms of Tamias, while T. harrisi differs from all the others in its much 

 smaller ears. Externally, however, there is not only a general similarity in 

 the pattern of coloration, but also in general form, while in cranial charac- 

 ters there is also a strong degree of similarity, these species agreeing in cer- 

 tain common cranial features, by which they are distinguished from the 

 restricted Spermopkili* 



* Tamias lateralis is, however, almost an exception, its cranial characters perhaps rather better 

 agreeing with one of the sections of Spermophilus than with Tamias. 



