AUNOLD-THK I'ALKONTOLDGV AND Sl'liATIOKAPUY OF SAN PEDRO. 143 



77. Tivela crassatelloides Conrad. 



Cytherea {Tri^onelUi) crassatclloiacs Qoti., ]o\.\x. Pliil. Acad. Sci., Vol. VII, 1837, [). 253. I'l. XIX, 



fig. 17. Hinds, Voyage Sulpher, p. 65, PI. XXI, fig. i, 1844. 

 Donax slultorum Marve, Linn., Lyst. Conch., pp. 37, 40, PI. IX, fig. 7, 1823. Gray, Index. Test. 



Suppi., PI. II (^Donax), fig. 2, 1828. 

 Cytherea crassatelloides Con., Hanley, Descr. Cat. Rec. Bivalve Shells, p. 106, 1S43. Sowkkby, 



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



PI. I, fig. 3, 1864. 

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

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

 Trigonia crassatelloides Con., Deshaves, Cat. Conch. Coll. B. M., Part i, p. 46, 1853. 

 Trigonia slultorum Gray, Deshaves, Cat. Conch. Coll. B. M., Part i, j). 46, 1853. 

 Pachydesma crassatelloides Con., Proc. Phil. Acad. Sci., 1854, p. 121. Cakpknter, Brit. Assn- 



Rept. 1863, p. 640; ^=Cytherea solidissivia Phii.., Gabu, Pal. Cal. Vol. II, ]). 96, 1869. 



Cooper, 7th. Ann. Rept. Cal. St. Min., 1888, p. 256. Keep, West Coast Shells, p. 



189, fig. 162, 1892. 

 Tivela crassatelloides Con., Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 187. 

 Cytherea {Tivela) crassatelloides CoN., Stearns, Proc. U. S. Nat. Mus., Vol. XXI, 1898, pj). 371- 



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



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

 e.xtremity shorter and more obtusely rounded than posterior; anterior dorsal margin nearly straight, 

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

 slope less than anterior; posterior e.xtremity narrower than anterior; three prominent, thick, c.irdinal 

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



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



The Plei.'jtoccne specimens li;ive a tendency toward more central umbones 

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

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



Common in the upper San Pedro series of San Pedro, Los Cerritos, Long 

 Beach, Crawfish George's and Dcadniiin Island; rare in the lower San Pedro series 

 of Deadnian Island. Found also in the Pleistocene of Twenty-sixth Street and S2)anitih 

 Bight, San Diego. 



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



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

 (Arnold). 



Genus Callista PiAi. 



Shell oval, transverse, inequilateral; pallial sinus suboval, profountl. 



Cytherea eryciua Linn, is a characteristic species. 



78. Callista newcombiana Gabb. 



Lioconcha newcombiana 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; 



