290 CALIFOKNIA ACADEMY OF SCIENCES. 



Family LXVII. TRIFORIDiE. 

 Genus Triforis Deshayes. 



Shell sinistral, sculptured, granular; whorls numerous, terminating below in a small aper- 

 ture, with tubular anterior canal; opposite this canal is sometimes a second one upon a varix, 

 marking the position of a former aperture. 



Triforis perversus Linn, is a characteristic species. 



313. Triforis adversa Montagu. 



Triforis adversa Mont., Test. Brit., p. 271, 1803. Cpr., Brit. Assn. Rept., 1863, p. 660. Tryon, 

 Man. Conch., Vol. IX, p. 187, PI. XXXIX, fig. 51, 1887. Keep, West Coast Shells, 

 p. 47. 1892- 

 Shell sinistral, with cancellated sculpture, caused by three spiral and numerous equally as 



prominent transverse ridges; resembles Bittiiini rugatum somewhat in sculpture. 



One imperfect specimen from lower San Pedro series at Deadraan Island 

 collected by Mrs. Oldroyd. 



Living. — Vancouver to Santa Barbara Island (Carpenter). 



Pleistocene. — San Pedro (Oldroyd). 



Superfamily CERITHIACEA. 

 Family LXVIII. CERITHIOPSIDiE. 



Genus Sella A. Adams. 



Shell spiral, elongated, many whorled, frequently varicose; aperture channeled in front, 

 with a less distinct canal posteriorly; outer lip not reflected; nuclear whorls sinistral; trans- 

 versely lirate. 



314. Seila assimilata C. B. Adams. 



Plate IV, Fig, 8. 



Cerithiopsis assimilata C. B. Ad., Maz. Cat., No. 563, 1852. Cpr., Brit. Assn. Rept., 1863, p. 660. 

 Tryon, Man. Conch., Vol. IX, p. 174, PI. XXXVI, fig. 59, 1887. Cooper, 7th Ann. 

 Rept. Cal. St. Min., 1888, p. 232. Keep, West Coast Shells, p. 48, 1892. 



Shell small, thin, turreted; nuclear whorls sinistral; whorls ten, ornamented with three 

 prominent, sharp, equal, equidistant, raised spiral lines; interspaces between ridges crossed by 

 numerous fine lirulse; suture indistinct, not distinguishable on upper portion of spire; base truncated 

 abruptly, flat; aperture subquadrate; outer lip thin, not efflise; inner lip simple; columella recurved; 

 canal short. 



Dimensions. — Long. 10 mm.; hit. 3.8 mm.; body-whorl 3.8 mm.; aperture 2.1 mm.; defl. 

 24 degrees. 



Resembles the Bittiums, but is distinguishable by the strong spiral lines. 

 Specimen identified by Dr. Dall. Rare in lower San Pedro series at San Pedro. 



