RISSOIDAE 137 



C. Interspaces with silky, wavy crinkles; 3 mm.; Coronado Islands 



cleo Bartsch 



Interspaces smooth, 3 mm.; CataHna Islands, south calif ornica Bartsch 



D. Whorls decidedly inflated; 3 mm.; Monterey south bakeri Bartsch 

 Whorls not inflated E 



E. W^ith very fine, numerous axial threads (48 to ^^ on last whorl) . F 

 With coarse riblets (36 on last whorl; 14 on next to last); 3 mm. Alaska 



to Monterey neivcovtbei Dall 



F. Shell slender; 2 mm.; San Pedro south dalli Bartsch 



Shell not as slender; 3.5 mm.; Redondo Beach south 



coronadoensis Bartsch 



Key to the Atlantic Coast Rissoina 



A. Shell sculptured with riblets or spiral lines B 



Shell smooth, glossy-white; 4 mm.; Carolinas, Florida, and West Indies; 



syn.: laevigata C. B. Ads. brouoniana Orbigny 



B. With axial ribs more prominent than spiral threads C 



With axial ribs not more prominent than spiral threads . . . . F 



C. Axial ribs only D 



Axial ribs and spiral threads both present E 



D. 4.5 to 6.0 mm.; white or stained yellow; 16 to 22 ribs; South Florida and 



the Wgsi Indies bryerea Montagu 



3.0 to 5.0 mm.; white; 1 1 to 14 ribs; suture sometimes deep; North Caro- 

 lina to Florida and the West Indies chesneli Michaud (PI. 2 2u) 



E. 4 to 5 mm.; ribs strong but disappearing on base; spiral threads strongest 



on base; white to rusty; southeast Florida and the \\ est Indies 



vndticostata C. B. Adams 

 6 to 7 mm.; 25 to 28 low, weak ribs, spirally striated or pitted between; 

 glossy; white to yellowish; North Carolina to the West Indies 

 deciissata Montagu 



F. Sculpture strongly cancellate G 



Not strongly cancellate; low, spiral threads dominant; axial ribs faint; 



weakly cancellate; 5 to 10 mm.; southeast Florida and the West 

 Indies striosa C. B. Adams 



G, 5 to 7 mm.; white; strongly cancellate; depressed interspaces large and 

 square; southeast Florida and the West Indies cancellata Philippi 



