ARNOLD — THE PALEONTOLOGY AND STRATIGRAPHY OF SAN PEDRO. 249 



The prevailing tvi)e of the iSaii IVnlio t'ostiil ypeciineiis does not correspond 

 exactly to any of the descriptions of tlie living varieties of this species as given by 

 Dr. Dall in the paper cited above. It conies nearest to var. nitispinosn, differing 

 from that form l)y having a straight canal. The name \i\r. pleistocenensis is suggested 

 for the !San Pedro fossil form. 



Rare in the upper San Pedro series of San Pedro; one specimen from lower 

 San Pedro series at Deadman Island. Fonnd also in the Pleistocene at Twenty- 

 sixth Street, San Diego. The specimen figured is from the upper San Pedro series 

 at San Pedro, and is now in the collection of Delos Arnold. 



Living. — California to Venezuela (Dall). 



Pleistocene. — San Pedro (Arnolil): San Diego (Dall; Cooper; Arnold): 

 Pacific coast of Lower California; head of the Gulf of California (Dall). 



248. Eupleura muriciformis var. curta, var. nov. 



Plate VIII, Fig. 9. 



Shell small, broadly fusiform; whorls four, angular, flat above, convex below; two sharp 

 spiral ridges on upper whorls, si.\' on body-whorl corresponding to obsolete spines on varix; one 

 prominent varix on body-whorl, other varices obsolete; whorls crossed by prominent, narrow, 

 rounded ridges, of which there are twelve on the penultimate whorl; aperture elliptical; outer lip 

 thickened by a row of six denticles; inner lip smooth, projecting; canal short, narrow. 



Dimensions. — Long. 15 mm.; lat. 10 mm.; body-whorl 11 mm.; aperture, including canal, 

 9.5 mm.; canal 2.2 mm.; defl. 65 degrees. 



Differs from E. muriciformis in having obsolete varices, transverse ridges 

 instead of nodes, much shorter canal, and in general much stronger sculpture. 



The type, which is figured, is from the upper San Pedro series at San Pedro, 

 and is now in the United States National Museum. 



Pleistocene. — San Pedro (Arnold). 



Genus Trophon Mont fori. 



Varices numerous, lamclliform or laciniated; spire prominent; aperture ovate; canal open, 

 usually turned to the left; shell white, often dark colored within the aperture. 



Trophon clathratas Linn, is a characteristic species. 



Subgenus Boreotrophon Fischer. 



249. Trophon (Boreotrophon) cerritensis, sp. nov. 



Platk VI, Fig. G. 



Shell of medium .size, elongate-fusiform, heavy; whorls six, angular, with angle in middle, 

 crossed by about eighteen strong, transverse ribs; lower portion of whorls ornamented with two or 

 three strong, spiral ridges, one of which is on the angle, the two systems of ridges giving a can- 

 cellated surface; body-whorl and columella cancellated; suture deeply impressed, distinct; aperture 



. -j^ , Marrli 24. 1903. 



