534 Proceedings of the national museum. vol.xxxh. 



CHLOROSTOMA (OMPHALIUS) DALLI var. SUBNODOSUS, new variety. 



Plate XL, fitiH. 6 and 6((. 



Description. — Similar to 0. dalli except that the transverse waves 

 are less pronounced and the spiral sculpture is somewhat coarser. A 

 more or less prominent ridge revolves about the umbilicus. 



Dimensions!. — Altitude, 10 mm.; latitude, 13.5 mm. 



Type.— C?it. No. 161985, U.8.N.M. 



Locality. — Head of Topanga Canyon, 3 miles south of Calabasas, 

 Los Angeles County, California. 



Horizon. — Lower Miocene. 



PLIOCENE SPECIES AND VARIETIES. 

 TEREBRATALIA OCCIDENTALIS Dall. 



Plate XLIX, figs. 6, 7, la, 8, 8*/, 9, and 9a. 

 Terebratalia occidentulii^ Dall, Proe. Cal. Acad. Sci., IV, 1871, p. 182, pi. i, fig. 7. 



Description. — Shell from subcircular to su))elliptical in outline, 

 rather thin; pedicle (lower) valve with mesial flexure concave; on each 

 side of this are usually two prominent ridges, and beyond these still a 

 second pair; surface of valve sometimes nearly smooth, but more 

 often with radiating ridges of var3dng prominence; lines of growth 

 usuall}' discernible, some being quite prominent; brachial (upper) 

 valve strongly mediall}^ convex, with one and sometimes two ridges 

 on either side; secondar}^ sculpture similar to that of lower valve. 

 Beak with a concave or flattened area on each side of the deltidium. 

 Shell broader proportionately in the younger stages of growth. 



Dimensions.- -LiOn^ixindiQ,., 27 mm.; latitude, 29 mm. 



Notes. — This variable species passes through the same mutations as 

 T. transversa Sowerb}^, from whicb it ditters by having the mesial 

 flexure of the pedicle valve concave and of the brachial valve convex 

 instead of vice versa as in T. transversa. Very abundant at Temescal 

 Canyon locality; also found recent on the Paciflc coast of North 

 America. 



Figured specimens.— C?ii. No. 164996, U.S.N.M. 



Locality. — Near the mouth of Temescal Canyon, 3 miles north of 

 Santa Monica, Los Angeles County, California. (Ralph Arnold and 

 J. J. Rivers). 



Horizon. — Recent and lower Pliocene, probably equiv^alent of mid- 

 dle Fernando formation. 



