154 University of California Publications in Geology [Vol. 13 



while 8. scopulosum has forty-five. In comparing the number of ribs 

 per 5 mm. on specimens of 8. trigenarium, n. sp., and 8. scopulosum 

 of about the same size, five ribs per 5 mm. are found in the former and 

 eight ribs per 5 mm. are found in the latter. Also the aperture of 

 S. trigenarium is more elongate posteriorly. 



Family Nassidae 

 Genus NASSA Lamarck 



NASSA WHITNEYI, n. sp. 

 Plate 7, figures 3 and 6 



Type.—'No. 12387; cotype— No. 12388, Univ. Calif. Mus. Pal. 



Shell medium sized; apical angle averages 53°; number of whorls to spire 

 five; sutures deeply depressed; whorls convex, with a fairly well marked tabu- 

 lation on the upper border; surface of body whorl ornamented with about 27 

 to 30 medium to coarse longitudinal ribs; surface also possesses 11 to 13 revolv- 

 ing ribs, which are more prominent and nearer together than the longitudinal 

 ribs; interspaces between revolving ribs much smaller than width of ribs; the 

 juncture of the two sets of ribs gives the surface a nodose aspect, but frequently 

 due to the lesser prominence of the longitudinal ribs, the spiral lines become 

 the more pronounced; on the spiral whorls only seven of the spiral ribs are seen; 

 outer lip sometimes possesses a rope-like varix; canal short, reflexed, and 

 separated from the posterior part of the body whorl by a deep, rounded depres- 

 sion; inner lip not preserved; columella appears to be smooth, but better 

 preserved specimens may show plications. 



Dimensions. — Type specimen U. C. no. 12387; alt., 14 mm.; greatest width, 

 9 mm. Cotype, U. C. no. 12388; alt., 13.5 mm.; greatest width, 7.8 mm. 



Occurrence. — This is a very common species throughout the entire Briones 

 formation. Type from U. C. loc. no. 3524; cotype from loc. no. 1176. 



Named in honor of Professor F. L. Whitney, Professor of Paleontology at 

 the University of Texas. 



This species differs from N. pabloensis Clark 28 in that it is more 

 convex and it possesses more numerous longitudinal and spiral ribs. 

 It differs from N. arnoldi Anderson 29 in that it is larger and it pos- 

 sesses more numerous and less prominent ribs. 



=s Clark, Univ. Calif. Publ. Bull. Dept. Geol., vol. 8, p. 493, pi. 65, figs. 8 and 

 9, 1915. 



29 Anderson, Proc. Cal. Acad. Sci., ser. 3, vol. 2. p. 204, pi. XVI, figs. 70 and 71, 

 1905. 



