ARNOLD — THE PALEONTOLOGY AND STRATIGRAPHY OF SAN PEDRO. 297 



Ceri/hidea sacrata G'L'D.,CvvL.,Y'roc. Zool. Soc, 1S56, p. 226. Keep, West Coast Shells, p. 71, 



fig. 56, 1S92. 

 Cerithidea californica Hald., Gabb, Pal. Cal, Vol. II, p. 79, 1869. Cooper, 7th Ann. Rept. Cal. 



St. Min., 1888, p. 233. Dall, Trans. Wagner Inst. Sci., Vol. Ill, Part 2, 1892, p. 277. 



Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1S92, p. 205. 



Shell turreted; ape.x decollated; whorls nine or ten, slightly convex, ornamented with three 

 or four spiral ridges and numerous transverse ridges, the two sets varying in prominence; suture 

 impressed, distinct; aperture subquadrate; outer lip effuse, thickened, broadly rounded below, and 

 slightly produced in a columellar beak; inner lip straight above this beak. 

 Dimensions. — Alt. 25 mm.; lat. 9.5 mm.; defl. 22 degrees. 



This is the only representative of this genus, and is one of the commonest of 

 the gastropods in the ujiper San Pedro formation. 



Found in the Pliocene of Deadman Island, lower San Pedro series of Dead- 

 man Island and San Pedro, and upper San Pedro series of Crawfish George's, Los 

 Cerritos, San Pedro, and Deadman Island. Found in the Pleistocene at Twenty- 

 sixth Street and Pacific Beach, San Diego. 



Living. — Paulinas Bay to San Diego; Mazatlan (Cooper). 



Pleistocene. — San Pedro to San Diego (Cooper): San Pedro; San Diego 

 (Arnold). 



Pliocene. — San Fernando, Los Angeles County (Cooi:)er) : San Pedro (Arnold). 



Family LXX. C^CID^. 



Genus Caecum Fleming. 



Young shell spiral in one plane, afterwards an arcuated tube, truncated posteriorly by the 

 loss of the spiral portion, and closed there by a convex septum or plug. 



CdBGum cornv.oides is a characteristic species. 



324. Cgecum californicum Dull. 



Plate VIII, Fig. 6. 



CcBcum cooperi CvR., Brit. Assn. Rept., 1863, p. 655; not of Smith {Jide Dall). 



Cceciwi californicum Dall, Proc. U. S. Nat. Mus., Vol. VIII, 1885, p. 541. Tryon, Man. Conch., 



Vol. VIII, p. 219, PI. LXVI, fig. 65, 1886. Keep, West Coast Shells, p. 73, 1892. 



Dall, Trans. Wagner Inst. Sci., Vol. Ill, Part 2, 1892, p. 299. 



Shell small, tubular, curved, white, very slightly tapering; plug bent toward conve.x side; 

 aperture circular, slightly contracted; surface ornamented by thirty to forty prominent, narrow, 

 rounded rings. 



Ditnensions.- — Long, (maximum) 3 mm.; lat. 0.9 mm. 



Shell may be distinguished from C. crebricinctum by its small size and much 

 more prominent, narrow, sharp rings. 



Quite common in the upper San Pedro series of San Pedro and Crawfish 

 George's, and in the lower San Pedro series of Deadman Island and San Pedro. 



( 38 ) April 27, 1903. 



