500 



University of California Publications in Geology [Vol. 8 



Localities and Positions. — From the Pliocene of Kirker Pass; also from the 

 Miocene at Walnut Creek, Contra Costa County, and Griswold's, Monterey 

 County, on the road to New Idria. 



T. ponderosum differs from T. carisaensis in that the spines are 

 less prominent, more numerous and do not stand out at right angles 

 to the surface of the shell but are turned upward; on some specimens 

 the spines become nearly obsolete ; the canal is not so long ; the spiral 

 ribbing is usually present on the body whorl as well as on the whorls 

 of the spire. It lacks the sinus or groove which is so marked on T. 

 carimoisis and which is situated about half way between the spinose 

 shoulder of the body whorl and the anterior end of the canal. 



Occurrence. — On the north side of Mount Diablo, T. ponderosum 

 and T. carisaensis Anderson are found in the same section, T. pon- 

 derosum being found at the top of the section while T. carisaensis is 

 found about two hundred feet below associated with a different fauna. 

 T. ponderosum is also found to the southeast of the town of Walnut 

 Creek, where it is found in nearly the same horizon as T. carisaensis. 



TEOPHON PONDEEOSUM Gabb var. PABLOENSIS, n. var. 

 Plate 66, figure 5 



Shell large ; spire low with three or four whorls ; body whorl very 

 ventricose ; sutures obscurely impressed ; surface of body whorl sculp- 

 tured by about twelve thin, lamella-like varices, which are more promi- 

 nent on the tops of the whorls, becoming quickly obscure anteriorly ; 

 whorls unangulated ; revolving ribbing not evident ; mouth opening 

 wide, semilunar ; outer lip sharp, slightly reflexed anteriorly ; inner 

 lip encrusted ; canal short, narrow and slightly twisted ; umbilical scar 

 long and subperforate. 



Only one specimen of T. ponderosum var. pabloensis, n. var., has 

 so far been found. More collecting may show that it should not be 

 separated as a variety; on the other hand, it may prove to be a dis- 

 tinct form worthy of being classed as a species. It differs from T. 

 ponderosum in that it is not spinose ; the whorls are not angulated, 

 and the spire is not so high. 



Dimensions. — Length of shell, about 61 mm. ; length of body whorl, 

 49 mm. ; greatest width of body whorl, 49 mm. 



Occurrence. — In the Upper San Pablo Group to the southeast of 

 the town of Walnut Creek, University of California locality 140. 



