232 CALIFOKNIA ACADEMY UF SCIENCES. 



wliile tliat of the lower wliorls woiiUl he about oiie-liall' of llial. Some of (he adult 

 shell!; also show a deflectiou of 50 doj^recs. The robust shells as a rule show more 

 transverse ridges than (lie slenderer foiins. Distinguishable fniiu var. cooperi by 

 less aiigulated whorls and ridges, less impressed suture, greater defleetion of upper 

 whorls, and larger size. The robust form somewhat resembles i\^. cdHfornumn, but 

 is distinguishable from that species by its appressed, rather than impressed suture, 

 less prominence of spiral litius, and smaller si/e. Dr. Dall pronounces this species a 

 precui-sor of N. cooperi. 



Rather common at Los Cerritos, where the type was found. One or two 

 specimens found in the upper San Pedro series at San Pedro, Long Beach, and 

 Crawfish George's. Found also in the Pleistocene at Spanish Bight, San Diego. 

 The specimen figured is the type, which came from the upper San Pedro series at 

 Los Cerritos, and is now in the United States National Museum. 



Pleistocene. — San Pedro; San Diego (Arnold). 



220. Nassa fossata Gould. 



Biicciman fossahim Gi.D., Proc. Bost. Soc. Nat. Hist., 1S50, p. 152. Otia, Conch., p. 67, 1S62. 



Nassa fossata Gld., H. & A. Adams, Gen. Rec. Mollusca. Cpr., Brit. Assn. Rtpt., 1863, p. 662. 

 Gabb, Pal. Cal, Vol. II, p. 74, 1869. Tryon, Man. Conch., Vol. IV, j). 55, PI. XVII, 

 fiRs. 316, 318, 1882. Cooper, 7th Ann. Rept. Cal. .St. Min., 18SS, p. 253. Keep, 

 West Coast Shells, p. 36, fig. 16, 1892. Williamson, Proc. U. S. Nat. Mus., Vol. XV, 

 1892, p. 212. 



Shell small, conical; spire elevated; apex subacute; whorls seven, convex; body-whorl 

 ventricose; ornamentation of fourth and fifth whorl consists of five or six strong-, nodose, spiral 

 ridges which increase in number by intercalation on the lower whorls; the prominence of the nodes 

 varies inversely with the number of ridges, the ridges on the body-whorl being nearly smooth and 

 alternating large and small; the ridges near the angle of the whorl reach the greatest promin'^nce; 

 suture deeply impressed, distinct; aperture ovate; outer lip thickened and denticulated by ends of 

 revolving internal ridges; inner lip incrusted, the incrustation spreading over part of body-whorl and 

 columella; columella short, curved, spirally striated, and grooved deeply next to body-whorl; anterior 

 sinus short, broad, recurved. 



Dimensions. — Long. 29 mm.; lat. 17 mm.; body-whorl 21 mm.; aperture, including canal, 

 14.5 mm.; defl. 50 degrees. 



The adolescent shell of this species resembles N. per-pingim, but may be 

 distinguished by the greater convexity of the body-whorl, greater deflection, and 

 general more solid a|)pearance. The adult shells are characterized by their general 

 solid appearance, great deflection, and the great difference in sculpture between the 

 upper and lower whorls. 



Found in the Pliocene at Deadman Island; in the lower San Pedro series at 

 Deadman Island and San Pedro, and in the upi)er San Pedro series at all of the 

 localities in the vicinity of San Pedro. Found also in Pleistocene at Spanish Bight 

 and Pacific Beach, San Diego; and at old inigaling ditch and Barlow's ranch, 



