1913J 



Merriam: Fauna of Orindan and Siestan 



383 



This form was originally described under the generic name of 

 Sigmogomphius , on the assumption that there were but three 

 superior cheek-teeth. In the original description, the writer 

 called attention to the similarity of the dentition to that of 

 Eucastor Leidy, but separated it from that genus owing to the 

 difference in pattern of the enamel folds. Comparative material 

 was not available at that time, and the writer was not aware of 

 the extent of change possible in the tooth pattern of these forms 

 with wear. There seems now good reason to believe that a worn 

 Sigmogomphius molar would develop a tooth pattern similar to 

 that of Eucastor, and that both Sigmogomphius and Eucastor are 

 not to be distinguished from the Old World genus Dipoides 

 Jager. It is, however, worth noting that the reduction of the 

 posterior molars in some of these forms suggests a possible reduc- 

 tion of the cheek-tooth formula to three, as was assumed for the 

 genus Sigmogomphius. It is not certain that this reduction 

 occurs in Dipoides lecontei, as the last molars may have been 

 lost from the type specimen. 



A single lower cheek-tooth. P 4 , (tigs. 9a and 9b) from the 

 Siestan beds resembles the European type of Dipoides, and the 

 tooth pattern shows close similarity to that of a somewhat larger 

 form found in the Thousand Creek beds of northern Nevada. 



LEPUS, sp. 



Fragmentary remains of two rabbits are known from fresh- 

 water beds in the hills near Berkeley. They consist of a lower 

 tooth (no. 19827), from the Siestan beds near Bald Peak, and 

 a portion of a lower jaw from an Orindan exposure in Wildcat 

 Canon. It is doubtful whether the two specimens represent 

 the same species, but neither one is cei'tainly specifically deter- 

 minable. 



PLANT REMAINS 



At several localities in the Siestan formation, imperfectly pre- 

 served plant remains have been found in clays and sands con- 

 taining fresh-water shells, a few land shells, and remains of 

 land vertebrates. The plant remains consist largely of fragments 

 of stems and leaves of rushes and grass, but include also a few 



