ARNOLD — THE PALEONTOLOGY AND STKATIGEAPHY OF SAN PEDRO. 205 



[S. D.] Drillia incisa Carpenter. 



Drillia incisa CpR., Brit. Assn. Rcpt., 1863, p. 657. Cooper, 7th Ann. Rept. Cal. St. Min., 

 1888, p. 239. 



Shell like D. inermis, except that the spiral sculpture consists of several impressed grooves. 



Found in the Pleistocene at Pacific Beach, San Diego. 



Living. — Straits of Fiica to Santa Cruz (Cooper). 



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



173. Drillia inermis Hinds. 



Plate V, Fig. 10. 



Pleurotoma inermis Hds., Proc. Zool. Soc, 1843, p. 37; Voyage Sulphur, p. 16, PL V, fig. 8, 1844. 

 Drillia inermis Hds., Cpr., Brit. Assn. Kept., 1863, p. 657. Gabb, Pal. Cal., Vol. II, p. 72, 1869. 



Tryon, Man. Conch., Vol. VI, p. 182, PI. XII, figs. 40 and 43; PI. XXXII, fig. 42, 



1884. Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 239. 



Shell elongate, slender; spire elevated; apex acute; whorls eight or nine, slightly angulated 

 a little posterior to middle, the posterior portion being slightly concave, and the anterior portion 

 slightly convex; ornamentation consists of nine to eleven rounded, spiral ridges, and numerous 

 prominent transverse ridges following th.e lines of growth, which are convexly angulated on the 

 angle of whorl; the ornamentation is more prominent on the lower portion of the whorls; suture 

 impressed, distinct; aperture elliptical; outer lip thin, arcuate anteriorly; posterior sinus shallow; 

 anterior sinus rather long; inner lip and inner portion of columella incrusted; columella slightly 

 recurved. 



Dimensions. — Long. 30 mm.; alt. 9 mm.; body-whorl 17 mm.; aperture, including canal, 

 II. 5 mm.; defl. 22 degrees. 



Distinguishable from D. penicillata by longer canal, angulation of whorls, and 

 greater prominence of ornamentation; distinguishable from D. cancellata by less 

 deflection and angulation of whorl, except body-whorl, which is more evenly convex 

 than in the latter. 



Rare in lower San Pedro series of Deadman Island, and in the upper San 

 Pedro series of Los Cerritos and San Pedro. The specimen figured is from the 

 upper San Pedro series at San Pedro, and is now in the collection of Delos Arnold. 

 Found in the Pleistocene at Barlow's ranch, and the old irrigating ditch, Ventura; 

 and at Spanish Bight and Pacific Beach, San Diego. 



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



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

 (Arnold). 



174. Drillia inermis var. penicillata Carpenter. 



Drillia penicillata CpR., Brit. Assn. Rept., 1863, p. 658; Jour, de Conch., Vol. XIII, 1865, p. 146. 

 Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 239. Keep, West Coast Shells, p. 56, 

 fig. 38, 1892. Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 208. 



Pleurototna penicillata Cpr., Tryon, Man. Conch., Vol. VI, p. 1S2, PI. XII, fig. 40, 1884. 



Shell elongated; spire elevated; apex acute; whorls eight, only slightly convex; ornamented 

 with numerous nearly obsolete, rounded, spiral ridges, and fine incremental lines which, reproducing 



