ARNOLD — THE PALEONTOLOGY AND STKATIGKAPHY OF SAN PEDKO. 319 



Shell conical, apex erect, nearly central, rather sharp, smooth; posterior surface straight; 

 anterior slightly convex; ornamentation of fine incremental lines, giving quite a rough surface to 

 some specimens; aperture oval to nearly circular; rim smooth. 



Dimensions. — Long. 31 mm.; lat. 27.5 mm.; alt. 19 mm. 



Easily (li.stin<!;nisliable by its elevated, nearly central apex, comparatively 

 smooth, light colored .surface, and its size. 



Not uncommon in the upper San Pedro series of Crawfish George's. 



Living. — Sitka to San Diego (Cooper): Half Moon Bay, San Mateo County 



(Arnold). 



Pleistocene. — Santa Barbara to San Diego (Cooper): San Pedro (Arnold). 



362. Acmgea paleacea Gould. 



Acmaa paleacea Gld., Bost. Jour. Nat. Hist., Vol. VI, 1S53, P- 376. PI. XIV, fig. 5; Mex. and Cal. 



Shells, p. 3, PI. XIV, fig. 5, 1853. Dai^i,, Am. Jour. Conch., Vol. VI, iSji.p. 253. 



Tryon, Man. Conch., Vol. XIII, p. 20, PI. VI, fig. 42, 189 1. Williamson, Proc. U. S. 



Nat. Mus., Vol. XV, 1892, p. 197. 

 Nacella paleacea Gld., Cpr., Brit. A.ssn. Rept., 1863, p. 650. Keep, West Coast Shells, p. 104, 1892. 



"Shell minute, delicate, thin, elongated, laterally compressed, so that the two sides are 

 parallel; dorsal aspect a long, narrow oval; lateral aspect low, triangular; apex at about the anterior 

 third, acute, antrorse; surface with delicate lines of growth and a few obtuse radiating ridges along 

 the dorsal slope at each end; color cinnamon brown." 



Dime7isions. — Long. 7 mm.; lat. r.5 mm.; alt. 2 mm. 



This shell has little resemblance to any of the others of its genus found in this 

 formation, and ma}' readily be distinguished by its small size and peculiar shape. 

 Dr. Dull itleiitified the specimen. 



Rare in the upper San Pedro series of Crawfish George's; two specimens found. 



Living. — Santa Barbara (Jewett): Monterey; San Diego (Dall). 

 Pleistocene. — San Pedro (Arnold). 



363. Acmaea pelta Eschscholtz. 



Acmaa pelta Esch., Zool. Atl., Vol. V, p. 19, No. 5, 1833. Cpr., Brit. Assn. Rept., 1863, p. 650. 

 Gabb, Pal. Cal., Vol. II, p. 52, 1869. Dall, Am. Jour. Conch., Vol. VI, 1871, 

 p. 246, PI. XIV, fig. 6. Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 228. Trvon, 

 Man. Conch., Vol. XIII, p. 17, PI. VIII, fig.s. 86-95, 1891- Keep, West Coast Shells, 

 p. 102, 1892. Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 197. 



Shell depressed, rounded, with few prominent bulging ribs, which are not developed in the 

 young shell; apex smooth, obtuse, and anterior to center. 



Two specimens sent to Dr. Dall were identified by him as the young of 

 this species. 



Rare in the lower San Pedro series of Deadman Island; and upper San Pedro 

 series of Los Cerritos and San Pedro. Found in the Pleistocene at Pacific Beach, 

 San Diego; and at Barlow's ranch, Ventura. 



