ARNOLD — THE PALEONTOLOGY AND STKATKiKAlMlY OF SAN PEDRO. 247 



oiilor lip.s, while others are Htronj;ly dentate. Of tll'ty spcciineiis from tlie San Pedro 

 Pleistocene only three have the characteristic tooth developed, thus sliowinj:; that in 

 these earlier forms this distinguishing characteristic was only occasional. The 

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

 spiratam of I'lainvillc. 



Found in all of the lower and upper Han 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). 



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

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



245. Monoceros lapilloides Conrad. 



Purpura {Motioceros) lapilloides Con., Jour. Phil. Acad. Nat. Sci., \'ol. VII, 1837, p. 265, PL XX, 



fig. 18. 

 Monoceros lapilloides CoN., = M. punctatum Gray, -\- M. brevidcns 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 witii 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. 



Dimensio7is. — Long. 20.5 mm.; lat. 13 mm.; body-whorl 18 mm.; aperture 14 mm.; dctl. 

 67 degrees. 



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

 guishable from J/, engonatuvi by much shorter spire, broader and shorter pillar, and 

 much less angular whorls; distinguishable from Purpura sa.dcoln by relatively larger 

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



Raz'e 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 Monoceros. 



Type, Chorus belcheri Hinds. 



246. Chorus belcheri Hinds. 



Murcx belcheri Hds., Proc. Zool. Soc, 1S43, 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, 



PI. 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. 



