PALEONTOLOGY ZORRITOS FORMATION 147 



One specimen of this interesting genus, in the Nelson 

 collection, undetermined by him, is apparently identical with 

 the European Amiantis incrassata var. ovoidalis Sacco, and 

 is accordingly referred to that variety. Comparison with 

 specimens of A. incrassata from the Eocene of France 

 shows clearly that the Peruvian form is of the same species, 

 and according to such varietal differences as have been 

 worked out it appears identical with var. ovoidalis Sacco, 

 from the Tongrian of the Italian Piedmont. The species as 

 a whole is common in the Eogene of Europe. 



To the author's knowledge only two species of Amiantis 

 are known from the North American Tertiary, A. callosa 

 Conrad, 164 from the Pleistocene and Recent of southern 

 and Lower California, and A. dalli^ from the upper San 

 Pablo Miocene of California, but both are dissimilar to 

 incrassata. 



The exact horizon of the Peruvian specimen is not known, 

 but it is highly probable that it came from one of the three 

 members of the Zorritos formation. 



Genus PITARIA Roemer 

 Subgenus HYSTEROCONCHA Fischer 



Section LAMEXUCONCHA Dall 



Pitaria (Lamelliconcha) planivieta (Guppy) 



PLATE X Fig. 6. 



Cytherea (Callista) planivieta Guppy, Quart. Jour. Geol. Soc. 

 Lond., vol. 22, p. 292, pi. 18, fig. 3, 1866. 



Callista planivieta (Guppy) Gabb, Trans. Am. Phil. Soc., n. s. 

 vol. 15, p. 250, 1873. 



Cytherea planivieta Guppy, Geol. Mag., dec. 2, vol. i, p. 442 (check 

 list) 1874. 



164 Jour. Ac. Nat. Sci. Phila., vol. 7, p. 252, 1837. 



165 Univ. Cal., Bull. Geol., vol. 8, p. 465, pi. 50, fig. 2, pi. 53, 



figs. 1-4, 1915. 



