merriam.] Sigmogomph{us Le Contei, 305 



fiber was formerly abundant in Europe and North America; it has, 

 however, within comparatively recent times, suffered destruction 

 through human agency to such an extent that its extinction is prob- 

 ably not far distant. In North America it was at one time found 

 over the greater portion of the continent from northern Mexico as 

 far north as the forest limit. It is now confined to the sparsely 

 inhabited and less frequented districts. In Europe the present geo- 

 graphical distribution of the beaver is limited to a single locality on 

 the river Elbe. 



Most of the ancient Castoridae were much smaller than the 

 living form, averaging about half its size. The single exception is 

 found in Trogontherium, which was somewhat larger than Castor. 



In the following description, and in the discussion of affinities, it 

 will be seen that the Californian Pliocene form bears an interesting 

 relation to those from the Upper Miocene and the Pliocene of other 

 portions of North America and Europe. 



DESCRIPTION. 



Sigmogomphins Le Contei* — Gen. et sp. nov. The posterior por- 

 tion of the skull was unfortunately so decomposed and undistin- 

 tinguishable from the black, clayey matrix that in preparation only 

 about one-half of the upper and two-thirds of the lower side could 

 be made out. Evidently the greater portion of the skull was there 

 originally, since the tympanic bullae and other parts of the posterior 

 end were present. The lower jaw could not be found. 



The anterior half of the cranium, of which the superior aspect 

 is shown in Fig. 1 , a, resembles very much that of Castor, or perhaps 

 still more the proportions of the bones in Steneofiber. The nasal 

 region resembles that of the other Castoroid forms. The incisors 

 are rather close to the upper molars. On the lower side the an- 

 terior palatine foramina appear to be largely, perhaps entirely, in the 

 premaxillaries, but run back to the suture between maxillary and 

 premaxillary. 



The superior molar series Fig. 1. b, consisting of three semipris- 

 matic teeth on each side, converge anteriorly as in most Castoridse. 

 As the number of molars is one of the important characters of the 



*Named for Prof. Joseph Le Conle. 



