New Spermojyhih from California. 31^ 



the dorsal strij)e. In one specimen (No. 4,720 $ ) the vermicula- 

 tions on the rump are much more distinct than in the others. 

 Sometimes there is a blackish stripe above the white stripe of 

 the upper eyelid. Sometimes there is a touch of rufous on the 

 outside of the ankle. In one specimen (No. 2,708 ? ) the tail is 

 considerably broader sub- terminally than toward the base. A 

 single individual (No. 4,7216) has the rufous dorsal band 

 duller and paler than in the others, though still sharply 

 defined. The posterior third of the sole is well covered with 

 hair, except in No. 4,719 ? , in which it is entirely naked — prob- 

 ably the result of unusual wear (the tail in the same specimen 

 is very shabby). Sometimes the dark basal portion of the fur 

 on the belly shows through. 



Cranial characters. — On comparing a series of skulls of Sper^ 

 mopJiilus beldmgi from Donner, California, with a correspond- 

 ing series of its nearest ally, 8. richardsoni townsendi, from 

 near Laramie, Wyoming, several excellent specific characters 

 may be seen. The most noticeable of these, viewing the skull 

 from above, is the great breadth of the interorbital plane of the 

 frontals, which projects well out over the orbits, and in adult 

 skulls is perforated by the supraorbital foramina. In young^ 

 skulls this foramen is incomplete externally, existing as a deep 

 notch. The average ratio of interorbital breadth to basilar 

 length in nine skulls of heldingi is 28.0; in two skulls of town- 

 sendi it is 22. 9. The premolar is very much larger in townsendi 

 than in leldingi, though it is by no means small in the latter. 

 It is the large size of this tooth in toiunsendi that gives the 

 molar series the relatively greater length shown in the table of 

 measurements of that species. In adult skulls of leldingi the 

 post-palatine foramina are situated wholly within the palatine 

 bones; in townsendi they are on the palato- maxillary suture. 

 In leldingi, compared with toivnsendi, more of the base of the 

 presphenoid bone is exposed behind the shelf of the palatine; 

 the foramen behind the last molar is conspicuously larger; the 

 foramen magnum is notably smaller, and its vertical diameter 

 is relatively as well as actually much shorter. This last peculiar- 

 ity is correlated with an actual difference in the posterior plane 

 of the skull, which is larger and more highly arched in town- 

 sendi than in heldingi. Even the under-jaw presents a strik- 



