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NO. 2183. NEW NORTHWEST AMERICAN BIVALVES— BALL. 395 



NUCULA PETRIOLA, new species. 



Shell minute, ovate, inflated, the form rescmblmg Crenella colum- 

 hiana, the prodissoconoh visible on the rather inflated beaks; lunula 

 obscure; color greenish oUve, smooth and polished; valve margins 

 smooth, hinge hue very short. Length, 1.25; height, 2; diameter, 

 1.5 mm. Cat. No. 271416, U.S.N.M. 



Off Santa Rosa Island, California, in 53 fathoms, mud. The soHd 

 shell and inflated form of this minute Nucula seem to indicate that it 

 is not an immature shell. 



LEDA NAVISA, new species. 



Shell elongate, arcuate, inequilateral, with slender recurved rostrum 

 and well-marked smooth impressed escutcheon but no lunule; base 

 oonvexly arcuate, rostrum obliquely truncate, anterior end evenly 

 rounded; beaks obscure, 5.5 mm. from the anterior end; sculpture of 

 numerous sharp concentric low ridges, with wider flat interspaces, 

 obsolete toward the rostrum; anterior teeth about twelve, posterior 

 about twenty, the resilifer mmute, subumbonal, not projecting; 

 interior chalky, a small medial ridge near the end of the rostrum. 

 Height, 7; length, 16; diameter, 5 mm. Cat. No. 208770, U.S.N.M. 



Off the Farallones Islands, California, in 191 fathoms, sand; bottom 

 temperature 44°. 5. 



LEDA AMIATA, new species. 



Shell light olivaceous, elongate, compressed, the posterior dorsal 

 margin nearly straight; beaks low, polished, about 3.5 mm. from 

 the anterior end, showing the whitish prodissoconch; the smooth sur- 

 face continues for a short distance when the sculpture changes to 

 sharply evenly lamellose with slightly larger interspaces wider on the 

 rostral area which is defined by the angular turn of the lamellae 

 which stop short at the sharp margin of the long impressed escutcheon; 

 interior porcellanous, with twelve anterior and sixteen posterior 

 teeth, the resilifer minute, subumbonal, hardly projectmg. Length, 

 11,3; height, 4,5; diameter, 3.0 mm. Cat. No. 209252, U.S.N.M. 



Station 4351, off San Diego, California, in 488 fathoms, muddy bot- 

 tom. This elegant shell recalls L. constellata of the Panama fauna, 

 but the rostrum is more simply sculptured. 



LEDA OXIA, new species. 



Shell minute, rounded in front, very acute behind, the valve end- 

 ing in a sharp point; base arcuate, beaks low, suboentral, dorsal 

 slopes nearly straight; sculpture of regular, equal concentric ridges 

 with subequal interspaces, a depressed ray from the beak to the base 

 anteriorly, a deeply impressed, concentrically striated escutcheon 

 bordered by a rounded keel; lunule Imear; about eight teeth on either 



