488 University of California Publications in Geology [Vol. 10 



nomic characters can be recognized in P 5 . On the basis of structure 

 of this tooth, the Hawver Cave material appears to pertain to a new 

 species. Comparisons have been made with the corresponding tooth 

 in skulls belonging to the Recent species Sylvilagus auduboni, Lepus 

 calif ornicus, L. campestris, and L. ivashingtoni klamathensis. 



Specimen 21437 is the anterior portion of a ramus with incisor 

 and P3 intact. In size and in length of lower diastema this jaw frag- 

 ment is evidently to be referred to Lepus rather than to Sylvilagus. 

 These characters serve also to distinguish no. 21437 from L. w. 

 klamathensis. In enamel pattern P3 of the cave specimen approaches 

 that in Sylvilagus auduboni most closely. The pattern differs, how- 

 ever, from that in the former by a deeper indentation of the outer 

 anterior border of the posterior re-entrant angle, while internally this 

 anterior border is less complex. In no. 21437 there is also a single 

 deep indentation of the posterior border toward the inner side, which 

 apparently distinguishes this form from Sylvilagus auduboni. 



Contrasted with corresponding teeth of Lepus calif ornicus, no. 

 21437 from Hawver Cave differs in greater complexity of enamel 

 border of the posterior re-entrant angle, particularly in those char- 

 acters already mentioned in a comparison of the fossil form with 

 Sylvilagus. In no. 18758 Calif. Mus. Vert. Zool. the indentation of 

 the outer, anterior border of the posterior re-entrant angle approaches 

 closely in appearance that in the cave tooth. There is certainly a 

 much greater similarity between no. 21437 and P3 of L. calif ornicus 

 than between the former and L. campestris. 



Measurements or no. 21437 



Length of lower diastema 



P5, greatest anteroposterior diameter 



P5, greatest transverse diameter 



Edentata 



The most conspicuous group of animals occurring in the Pleisto- 

 cene deposit of Hawver Cave is that of the gravigrade edentates or 

 ground-sloths. Both the Megalonychidae and the Mylodontidae are 

 represented ; the former family by skull and skeletal material of 

 Nothrotherium and a single element doubtfully referred to Megalonyx, 

 and the latter family by several characteristic structures referred to 

 Mylodon. 



It is interesting to note the relative abundance of these forms in 

 the cave fauna as indicated by actual numbers of individuals and 



22.8 mm. 

 3.2 

 2.6 



