ARNOLD — THE PALEONTOLOGY AND STKATUiUAPIIY OF SAN PEDUO. 247 



outer lips, while othei-s are strongly dentate. Of lift}' specimens from the San Pedro 

 Pleistocene only three have the characteristic tooth developed, thus showinj^ that in 

 these earlier forms this distinj^uishing characteristic was only occasional. The 

 scaly specimens are generally the strongest keeled. This latter form is the var. 

 sj)iratu?n of Blainville. 



Found in all of the lower and upper San Pedro series localities in the vicinity 

 of San Pedro. Found also in the Pleistocene at Barlow's ranch, Ventura; and at 

 Pacific Beach, San Diego. 



Living. — Baulinas Bay to San Diego (Cooper). 



Pleistocene. — San Pedro; San Diego (Cooper) : Lake Merced, San Mateo 

 County; San Pedro; Sau Diego; Ventura (Arnold). 



245. Monoceros lapilloides Conrad. 



Purpura {Motioceros) lapilloides CoN., Jour. Phil. Acad. Nat. Sci., Vol. VII, 1S37, p. 265, PI. XX, 



fig. 18. 

 Motioceros lapilloides CoN., = M. piinctatitm Gray, -\- M. brevidens Con. {fide Cpr., Brit. Assn. 



Rept., 1863, p. 663). Keep, West Coast Shells, p. 28, fig. 9, 1892. Cooper, Bull. 



No. 4, Cal. St. Min. Bureau, 1894, Part 3, p. 28. 



Shell of medium size, purpuroid-shaped; spire elevated; apex subacute; whorls four, very 

 slightly convex; surface ornamented with nearly obsolete spiral cinguli and nearly obsolete, irregular, 

 wavy, transverse ridges; suture impressed, indistinct; aperture subovate; outer lip thickened, dentate; 

 inner lip flattened, smooth; canal short. 



Dimetisions. — Long. 20.5 mm.; lat. 13 mm.; body-whorl 18 mm.; aperture 14 mm.; defl. 

 67 degrees. 



The specimen described shows the reddish color of the live shells. Distin- 

 guishable from J/, engonatum by much shorter sjiire, broader and shorter pillar, and 

 much less angular whorls; distinguishable from Purpura mxicolu by relatively larger 

 spire, narrower aperture, dentate outer lip and spiral cinguli. 



Rare in upper San Pedro series of San Pedro; one specimen. 



Living. — Santa Barbara to San Diego (Carpenter): Monterey (Cooper). 



Pleistocene. — San Pedro (Arnold): Ventura County (Bowers). 



Genus Chorus Gray. 



Shell laminately varicose; spinose on the shoulder; canal rather long; outer lip with a spine 

 as in Motioceros. 



Type, Chorus belcheri Hinds. 



246. Chorus belcheri Hinds. 



Murex belcheri Hds., Proc. Zool. Soc, 1843, p. 127; Voyage Sulphur, PI. II, figs. 1-3, 1844. 



Pfeiffer, Nov. Conch., Ser. II, p. 35, PI. X, figs. 6, 7. 

 Chorus belcheri Hds., Cpr., Brit. Assn. Rept., 1863, p. 663. Tryon, Man. Conch., Vol. II, p. 198, 



Pl. LXI, fig. 309, 1880; Syst. Conch., Vol. II, p. 114, PI. XLV, figs. 43, 44, 1883. 



Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 235. Keep, West Coast Shells, p. 25, 



fig. 7, 1892. Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 216. 



