174 University of California Publications in Geology [Vol. 11 



Genus AMPHISSA H. and A. Adams 

 AMPHISSA PULCHEILINEATA, n.sp. 

 Plate 21, figures 5 and 6 

 Type specimen 11276, Coll. Invert. Palae. Univ. Calif., loc. 3055 



Shell medium in size; apex acute; whorls rather strongly and regularly convex: 

 sutures depressed ; number of whorls six or seven ; body whorl only a little over 

 half the height of the shell. Surface sculptured by rather fine longitudinal and 

 spiral ribbing, the former being considerably the heavier and separated by inter- 

 spaces somewhat wider than the ribs, about twenty in number ; on the spire seven, 

 and on the body whorl about fourteen of the spiral ribs, separated by inter- 

 spaces which average about twice the width of the ribs. Canal short, straight. 

 Convexity of body whorl between base and sides rather sharp ; on some specimens 

 there is almost an angulation along this line. Aperture not exposed. 



Dimensions. — Height, about 15 mm. ; height of body whorl, 8 mm. ; greatest 

 diameter of body whorl, 7 mm. 



Occurrence. — This species has been found only at the type locality, which is 

 in the Concord formation above the Kirker tuff beds. 



Family Nassidae 

 Genus MOLOPOPHORUS Gabb 

 MOLOPOPHOEUS BIPLICATUS (Gabb) 

 Plate 20, figures 4, 6 and 8 



Cuma Mplioata Gabb, Geol. Surv. Calif., Palaeontology, vol. 2, j>. 9, pi. 2, 



fig. 14, 1868; also p. 75, 1868. 

 Cuma biplicata Gabb, Arnold, U. S. Geol. Surv., Prof, paper no. 47, p. 19, 



1906. 



Cuma biplicata Gabb, Smith, Proc. Calif. Acad. Sci., ser. 4, vol. 3, pp. 

 165, 175, 1912. 



Molopophorus biplicatus Gabb, Clark, Univ. Calif. Publ., Bull. Dept. Geol., 



vol. 9, no. 2, p. 15, 1915. 

 Molopophorus gabbi Dall, Clark, op. cit., pp. 15, 18. 



This species is very similar to Molopophorus gabbi Dall, described 

 from the Lower Oligocene of Oregon. The two species are undoubt- 

 edly very closely related; the details of their sculpturing are prac- 

 tically identical ; there is a little difference in outline, M . biplicatus 

 being slightly more excavated below the collar on the body whorl. 

 For the reason that there can be very little doubt but that the species 

 are very closely related genetically, the writer proposes to consider 

 M. gabbi as a subspecies of M. biplicatus. 



