166 University of California Publications in Geology [Vol. 7 



with Recent specimens from the collection of the California 

 Museum of Vertebrate Zoology, which correspond to the fossil 

 forms in stage of wear of the teeth, and are therefore considered 

 to be of comparable age. 



Measurements 



No. 11264 No. 1407* 



Least temporal breadth 13. mm. 15. 



Anterior width between premaxillaries 11. 13.6 



Anterior width of palate at P 3 8.3 9.1 



Posterior width of palate back of M 3 8.2 9.1 



Length of upper tooth row 11.7 11.9 



Anterposterior diameter of auditory bullae 12.3 11.2 



Transverse diameter of auditory bullae 8.4 11.2 



No. 12404 No. 3183* 



Length of lower tooth row 11.8 mm. 11. 



Anteroposterior diameter of P 4 2.5 2. 



Anteroposterior diameter of M x 2.5 2.3 



Anteroposterior diameter of M 2 2.8 2.5 



Transverse diameter of P 4 2.2 2.1 



Transverse diameter of 3. 2.7 



Transverse diameter of M 2 3.2 3. 



* Calif. Mus. Vert. Zool. 



PEEOMYSCUS GAMBELI (Baird)? 

 This genus is represented by only one specimen, a right ramus 

 of the lower jaw, with M x . It is a small form near the size of 

 P. gambeli, the smallest of the Peromyscus species. 



MICEOTUS CALIFOENICUS (Peale) 

 This species is represented by abundant material. One of the 

 distinguishing skull characters of M. calif ornicus is the form of 

 the incisive foramina, which are of uniform width, instead of 

 narrowing anteriorly or posteriorly as in other species. In one 

 specimen, no. 18700, a portion of the skull, the incisive foramina 

 are of this shape. Other specimens referred to this species are 

 the anterior portions of a right and left ramus of the lower jaw 

 with P 4 and incisor; two right rami with incisor and condyle; 

 the anterior portion of a left ramus with incisor ; one with incisor 

 and and M 2 ; and a portion of a skull with palate and M 2 and 

 M 3 on either side. 



