ARNOLD — THE PALEONTOLOGY AND STRATIGRAPHY OP SAN PEDRO. 143 



77. Tivela crassatelloides Conrad. 



Cytherea {'I'rii^onel/a) cnissa/elioides Coii., ]m\r. Phil. Acad. Sci., Vol. VII, 1S37, j). 253, PI. XiX, 



tlj^. 17. Hinds, Voyage Sulpher, \). 65, PI. XXI, fij^. i, 1844. 

 Donax stultoruDi Mauvil, Linn., Lyst. Conch., pp. 37, 40, PI. IX, fig. 7, 1823. Gray, Index. Tt-st. 



Suppl., I'l. II l^Donax), fig. 2, 182S. 

 Cytherea crassatelloides Con., Hanley, Descr. Cat. Rec. Bivalve Shells, p. 106, 1843. Sowf.rhy, 



Thes. Conch., Vol. II, p. 612, PI. CXXVII, figs. 1-3. Reeve, Icon. Conch., Vol. XIV, 



PI. I, fig. 3, 1864. 

 Cytherea stultorum Gray, Hanley, Descriptive Cat. Rec. Bivalve Shells, p. 106, 1843. 

 Trigonella crassatelloides CoN., Jour. Phil. Acad. Sci., Vol. I, 1849, P- 213. 

 Trigonia crassatelloides Coti., Deshayes, Cat. Conch. Coll. B. M., Part i, |). 46, 1S53. 

 'I'rii^otiia stultorum Gray, Deshayes, Cat. Conch. Coll. B. M., Part i, ]>. 46, 1853. 

 Pachydesma crassatelloides CoN., Proc. Phil. Acad. Sci., 1854, p. 121. Carpenter, Brit. Assn- 



Rept. 1863, p. 640; =Cytherea solidissima Phil., Gabb, Pal. Cal. Vol. II, p. 96, 1869. 



Cooper, 7th. Ann. Rept. Cal. St. Min., 188S, p. 256. Keep, West Coast Shells, p. 



189, fig. 162, 1892. 

 Tivela crassatelloides Con., Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 1S7. 

 Cytherea {Tivehi) crassatelloides Con., Stearns, Proc. U. S. Nat. Mus., Vol. XXI, 1898, i)p. 371- 



378, PI. XXIII-XXV. Stearns, Nautilus, Vol. XIII, 1899, p. 73. 



Shell large, subequilateral, trigonal, depressed, thick; umbones subcentral, small; anterior 

 extremity shorter and more obtusely rounded than posterior; anterior dorsal margin nearly straight, 

 slopes down obliquely from umbo ; posterior dorsal margin slightly concave in fi-ont of umbo, 

 slope less than anterior; posterior extremity narrower than anterior; three prominent, thick, cardinal 

 teeth in each valve, anterior lateral tooth elongated; pallial sinus short, angular. 



Dimensions. — Long. 80 mm.; alt. 55 mm.; diam. 30 mm. 



The Plei.stocene specimens Ii;ive ti tendency towanl more central umbones 

 than do tlie living forms. This species is distinguishable from the Mactras by its 

 very thick shell and heavy cardinal teeth. Specimens identified by Dr. Dali. 



Common in the upper San Pedro series of San Pedro, Los C'erritos, Long 

 Bead), Crawfish George's and Deadman Island; rare in the lower San Pedro series 

 of Deadman Island. Found also in the Pleistocene of Twenty-sixth Street and Spanish 

 Bight, San Diego. 



Living. — Santa Cruz to San Diego (Cooper). 



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

 (Arnold). 



Genus Callista Poli. 



Shell oval, transverse, inequilateral; i)allial sinus suboval, profound. 



Cytherea enjcina Linn, is a characteristic species. 



78. Callista newcombiana Gabb. 



Lioconcha newcojnbiana Gabb, Proc. Cal. Acad. Sci., 1865, p. 189; Pal. Cal., Vol. II, p. 96, 1869. 

 Callista newcombiana Gabb, Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 231. Williamson, 

 Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 187, PI. XXIII, fig. 4. 

 Shell thin, trigonally ventricose, polished, marked by minute concentric striae; beaks large, 

 subcentral; anterior end prominent, narrowly rounded; posterior end a little the widest; base arcuate; 



