2 PALAEONTOLOGY OF CALIFORNIA. 



Locality and position: From the Miocene, in a boulder near Griswold's, in the 

 Coast Eange, on the road to New Idria. 



But a single specimen was found in a boulder, associated with Pecten caurinus, 

 Area microdonta, &c., and some other species, mostly indeterminate. I could 

 detect no trace of the terminal septum, but this may be due to the extreme thin 

 ness of the shell and a portion of the interior being filled with crystals. 



TROPHON, Montf. 



T. PONDEROSUM, 11. 8. 

 PI. 1, Fig. 3. 



SHELL moderate in size, robust, thick; spire sub-elevated; 

 whorls five, angulated in the middle, sloping above; suture 

 irregularly impressed. Surface marked by eight or nine blunt 

 varices, prominent and acute on the angle of the whorl, and com 

 monly becoming more or less obsolete above and below; in the 

 upper whorls the varices are replaced by mere elevated ribs, 

 which become smaller until in the first three volutions they barely 

 exist as undulations. Aperture broad; canal open, short, slightly 

 recurved; columellar lip heavily incrusted ; outer lip entire, sub- 

 acute. Umbilicus well marked, but closed. 



Figure, natural size. 



Localities and positions: From the Pliocene of Barker's Pass; also from the 

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

 County, on the road to New Idria. 



This fine species resembles somewhat T. Belcherii, Hinds, now living on the 

 Coast, but can be at once distinguished by its smaller size, lower spire, broader 

 and more robust form, and by the number and character of the varices. Some 

 very much mutilated specimens from Griswold's, probably referable to the present 

 species, have a row of prominent tubercles on the body whorl about half an inch 

 below the angle. 



