ARNOLD — THE PALEONTOLOGY AND STKATIGRAPHY OF SAN PEDRO. 315 



suddenly turns under to umbilicus; surface ornamented with fine, oblique incremental lines; suture 

 distinct, but not impressed; aperture semilunar; lip thin; columella incrusted, the incrustation 

 extending down and completely covering the umbilicus. 



Dimensions. — Long. 20 mm.; lat. 24 mm.; aperture 16 mm. x 10 mm.; defl. 130 degrees. 

 (A rather small specimen.) 



The young shells are more depressed than the adults, some of tlieni being 

 quite flat. In some of the specimens the callus has not completely covered the 

 umbilicus, leaving a little pit near the lower part of the umbilical region. This 

 sjiecies is very variable in both size and shape. Dr. Dall has described a variety 

 with an elevated spire which he calls var. alta. This variety is quite common in all 

 of the upper San Pedro series localities. 



Common in the upper San Pedro series of the San Pedro region, but rare in 

 tlie lower San Pedro series and Pliocene. Found in the Pleistocene at Barlow's 

 ranch and old irrigating ditch, Ventura; at Spanish Bight, Twenty-sixth Street, and 

 Pacific Beach, San Diego; and in the Pliocene at Pacific Beach, San Diego. The 

 specimen figured is from the upper San Pedro series at San Pedro, and is now in the 

 collection of Delos Arnold. 



Living. — Monterey to Lower California (Cooper). 



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

 Barbara; San Diego (Arnold). 



Pliocene. — Santa Barbara; San Fernando (Cooper) : San Pedro; San Diego 

 (Arnold): San Diego well (Dall). 



Miocene. — Martinez; Walimt Creek; Santa Inez; Santa Monica; Death 

 Valley (Cooper). 



Subgenus Lunatia Gray. 



Shell usually somber colored; covered with a dark, thin epidermis; not so thick as the 

 typical group; umbilicus open, without funiculum. Operculum corneous. 



Type, Natica ampullaria Lam. 



355. Polynices (Lunatia) lewisii Gould. 



Plate X, Fig. 14. 



Natica lewisii Gld., Proc. Bost. Soc. Nat. Hist., 1847, p. 239; Wilkes' E.xpl. Exped., p. 211, 



PI. XV, p. 253, 1852. 

 Lunatia lewisii Gld., Cpr., Brit. Assn. Rept., 1863, p. 661. Gabb, Pal. Cal., Vol. II, p. 77, 1869. 



= N. reiniana Dunker (young), ^ N. algida Gld. (^fide Trvon, Man. Conch., 



Vol. VIII, p. 35, PI. XIII, figs. II, 12; PI. IX. fig. 70, 1886). Cooper, 7th Ann. Rept. 



Cal. St. Min., 1888, p. 247. Keep, West Coast Shells, p. 45, fig. 25, 1892. Dall, 



Trans. Wagner Inst. Sci., Vol. Ill, Part II, 1892, p. 374. 

 Natica (Lujiatia) /^zfwzV Gld., Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 211. 



The adult may be distinguished from Neverita recluziana by its large size, 

 open umbilicus, generally more elevated spire, and a shallow, spiral groove near the 



