320 CALIFORNIA ACADEMY OF SCIENCES. 



Living. — Sitka to San Diego (Cooper). 



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

 (Arnold). 



364. Acmaea spectrum (Nuttall) Reeve. 



Acmesa spectrum Nutt., Rve., Cpr., Brit. Assn. Rept., 1863, p. 650. 



Acmtza spectrum NuTT., Gabb, Pal. Cal., Vol. II, p. 86, 1869. Cooper, 7th Ann. Rept. Cal. St. 



Min., 1888, p. 228. Keep, West Coast Shells, p. 100, figs. 86, 87, 1892. Williamson, 



Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 197. 

 Acmcea spectrum RvE., Dall, Am. Jour. Conch., Vol. VI, 1871, p. 251, PI. XIV, fig. 10. Tryon, 



Man. Conch., Vol. XIII, p. 14, PI. I, figs. 7-9, 1891. 



Shell depressed, with rather acute ape.x, which is about one-third length of shell ft"om the 

 anterior margin; ribs very prominent and rugose, generally alternating large and small. 

 Dimensions. — Long. 26 mm.; lat. 19 mm.; alt. 10 mm. 



The commonest of the Acmsedse, and easily distinguishable by the prominent, 

 rugose ribs. 



Rare in the lower San Pedro series of Dead man Island; and rather common 

 in the upper San Pedro series of Deadman Island and San Pedro. 



Living. — Bodega Bay to Lower California (Dall). 



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



Family LXXXI. LIOTIIDiE. 

 Genus Delphinoidea Broun. 



Shell orbicular, depressed, widely umbilicated; spire short; whorls transversely striated or 

 cancellated; aperture round, not nacreous; peristome continuous, simple. 



Delpldnoidea canceUata Marryat is a characteristic species. 



[S. D.] Delphinoidea coronadoensis, sp. nov. 



Shell minute, orbicular, depressed, milk-white, rather thick for size of shell; spire flattened 

 beneath plane of upper periphery of the body-whorl; whorls two and one-half, nearly circular in 

 cross-section; surface ornamented by numerous subequal, rounded spiral ridges, and very minute 

 transverse lines, the whole giving the surface a cancellated appearance; irregular lines denoting 

 interruption in growth are common on the body-whorl; suture deeply appressed; umbilicus wide, 

 deep; aperture suboval; peristome continuous, rather thick, slightly effuse. 



Dime)isions . — Ma.ximum diam. 2 mm.; alt. 0.9 mm. 



This specie.s, which is the smallest gastropod found in the Spanish Bight 

 Pleistocene, is named for the Coronado peninsula, into which Spanish Bight extends. 



Pleistocene. — San Diego (Arnold). 



