ARNOLD — THE PALEONTOLOGY AND STRATIGRAPHY OF SAN PEDRO. 329 



Genus Calliostoma Suuinson. 



Shell trochiform, conical, not unibilicated; last whorl angulated and usually ribbed at the 

 periphery; aperture quadrangular; columella simple, oblique, often ending in a tooth in front. 



Calliostoma zizyphinvm Linn, is a ciiaracteristic species. 



380. Calliostoma annulatum Martyn. 



Trochus annulatiis Mart., Univ. Conch., Vol. I, fig. 33, 1784. Philippi, Conch. Cab., p. 11, 



PL III, figs. 3, 4. 

 Zizyphiniis annulatus Mart., A. Ads., Proc. Zool. Soc, 1851, p. 164. Gray, Dieffenbach's 



N. Zealand, p. 237, No. 72. 

 Calliostoma annulahmi Mart., Cpr., Brit. Assn. Rept., 1863, p. 652. Gabb, Pal. Cal., Vol. II, 



p. 83, 1S69. Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 231. Tryon, Man. 



Conch., Vol. XI, p. 363, PI. LXVII, fig. 43, 1889. Keep, West Coast Shells, p. 79, 



fig. 64, 1892. Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, PL XXII, fig. 2. 



Shell conical; whorls seven, slightly angulated in center, and ornamented with sharply 

 nodose spiral ridges which increase by intercalation from two on third whorl to seven or eight on 

 body-whorl; suture deep, distinct; body-whorl acutely angulated at base; base nearly flat, ornamented 

 with, numerous smooth, rounded spiral lines; aperture subquadrate; columella nearly straight, 

 thickened. 



Dimensions. — Alt. 17 mm.; lat. 16 mm.; defl. 67 degrees. 



Distinguishable by slightly angulated whorls, nearly equally prominent nodose 

 ridges, and nearly straight cohimella. 



Quite rare in the upper San Pedro series of San Pedro. 



Living. — Straits of Fuca to San Diego (Cooper). 



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



Pliocene. — San Diego well (Dall). 



381. Calliostoma canaliculatum Martyn. 



Trochus canaliculatus Mart., Univ. Conch., Vol. I, fig. 32, 1784. 



Zisyphinus canaliculatus Mart., Gray, Dieffenbach's N. Zealand, p. 327. Reeve, Conch. Icon., 



fig. 18. 

 Calliostoma canaliculatujn Mart., Cpr., Brit. Assn. Rept., 1863, p. 652. Gabb, Pal. Cal., Vol. II, 



p. 83, 1869. Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 231. Tryon, Man. 



Conch., Vol. X, PL XLI, fig. 34, 1888; VoL XI, p. 361, PL LXVII, fig. 49, 1889. 



Keep, West Coast Shells, p. 80, fig. 65, 1892. Williamson, Proc. U. S. Nat. Mus., 



Vol. XV, 1892, PL XXII, fig. 6. 



Shell conical; whorls six, flat, ornamented with very prominent rounded, spiral ridges, two 

 on the third and fourth whorls, and then increasing by intercalation until the body-whorl in some 

 specimens has five or six prominent ridges, with a less number of auxiliary riblets in between; suture 

 deeply impressed, forming a canal; aperture subquadrate; base flat, and ornamented in the same way 

 as the whorls; lip as in C. costatinn. 



Dimensions. — Long. 19 mm.; lat. 20 mm.; defl. 67 degrees. 



Distinguishable by flat whorls, sutural canal, and few large spiral ridges. 



( 42 ) April 29, 1903. 



