AKNOLD — THE PALEONTOLOGY AND STUATIGKAl'HY OF SAN PEDRO. 235 



portion of aperture ridged by spiral sculpture; outer lip tliiii; inner lip thinly iiicrusted; columella 

 twisted and spirally ornamented; groove on upper part of columella prominent; canal short, curved. 

 Dimensions. — Long. 23 mm.; lat. 12.3 mm.; body-whorl 15 mm.; aperture, including canal, 

 II mm.; defl. 40 degrees. 



The transverse ornamentation is the most prominent in tlic iiiiper wliorls, 

 wliile in the later ones the spiral ridges are the most important. On the body-whorl 

 the tranverse ridges sometimes become nearly obsolete, being represented only by 

 lines of growth. 



Common in the upper and rare in the lower San Pedro series at San Pedro 

 and vicinity. Also found in the Pliocene at Deadman Island and Timm's Point. 

 Found in the Pleistocene at Spanish Bight and Pacific Beach, San Diego; and at the 

 old irrigating ditch and Barlow's ranch, Ventura. 



Living. — San Francisco to San Diego; Lower California (Cooper). 



P&i's^ocene.— Santa Barbara to San Diego (Cooper): San Pedro; Ventura; 

 San Diego (Arnold). 



Pliocene. — San Diego well (Dall) : San Pedro (Arnold). 



Miocene. — Santa Monica and Aliso Creek, Los Angeles County (Cooper). 



225. Nassa tegula Reeve. 



Nassa tegula RvE., Icon. Conch., Nassa, No. 98, PI. XV, 1853. Cpr., Brit. Assn. Rept., 1863, 

 p. 662. Gaeb, Pal. Cal., Vol. II, p. 74, 1869. Trvon, Man. Conch., Vol. IV, p. 39, 

 PL XIII, figs. 166, 167, 1882. Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 253. 

 Keep, West Coast Shells, p. 37, fig. 17, 1S92. Dall, Proc. U. S. Nat. Mus., Vol. XV, 

 1892, p. 213. 



Shell small, conical; spire elevated; ape.x subacute; whorls five, slightly angulated at middle, 

 with nine or ten prominent transverse ridges most prominent on angular part of whorl; these ridges 

 are sometimes divided by spiral grooves into two or more nodes; suture impressed, distinct; aper- 

 ture subquadrate; outer lip thickened by a row of elongated denticles; inner lip smooth and incrusted, 

 the incrustation spreading over the columella and the front of the shell like an apron; a rather shallow 

 groove separates the lower portion of columella from body-whorl; canal very short. 



Dimensions. — Long. 11 mm.; lat. 7 mm.; body-whorl 7.9 mm.; aperture, including canal, 

 5 mm.; defl. 58 degrees. 



The most robust of the N'ussas found in this locality. Distinguishable by 

 the prominence of the incrustation on the inner lip. Dr. Dall says that this species 

 is close to N. vibex of the Atlantic coast. 



Rare in the upper San Pedro series at San Pedro, Los Cerritos, Long Beach, 

 Deadman Island, and Crawfish George's; also occasionally found in the lower San 

 Pedro series at Deadman Island and San Pedro. Found also in the Pleistocene at 

 Twenty-sixth Street and Spanish Bight, San Diego. 



Licing. — Santa Barbara to San Diego; Lower California (Cooper). 



Pleistocene. — Santa Barbara to San Diego (Cooper): San Pedro; San Diego 

 (Arnold). 



