NO. 2183. NEW NORTHWEST AMERICAN BIVALVES— BALL. 399 



YOLDIA BERINGIANA, new species. 



Shell large, thin, smooth, except for lines of growth, brilUantly 

 polished, inequilateral, hardly rostrate, rounded at each end, less 

 compressed behind than Y. secuvda; color a rich yellowish brown^ 

 shghtly olivaceous near the umbones; valves closing completely; 

 escutcheon striated, narrower than in secunda; beaks very low, 24 

 anterior and 17 posterior teeth, the resUifer ample, cup-shaped, pro- 

 jecting. The pallial sinus is rather large and rounded. Length, 40; 

 height, 22; diameter, 16 mm. Cat. No. 226195, U.S.N.M. 



Station 3607, Bering Sea, off the Pribiloff Islands, in 987 fathoms, 

 mud. 



YOLDIA ORCIA, new species. 



Shell small, thin, pale olive, brilliantly polished, smooth, equilat- 

 eral; base deeply arcuate; beaks not prominent, the posterior end 

 shghtly compressed, pointed and attenuated, the anterior end rounded; 

 hinge with 8 anterior and 6 very minute posterior teeth, the resHifer 

 subumbonal, extremely small. Length, 4.5; height, 3.5; diameter 

 2 mm. Cat. No. 111420, U.S.N.M. 



Station 2923, off San Diego, California, in 822 fathoms, mud. 



This species has no indication of lunule or escutcheon. 



YOLDIA SANESIA. new species. 



Shell small, thin, plump, pale olivaceous, inequilateral, the anterior 

 end shorter, the beaks 2.6 mm. behind it; base roundly arcuate, dorsal 

 slopes nearly straight, anterior end rounded, posterior end shghtly 

 recurved, compressed and bluntly rounded; beaks low, inconspicuous, 

 with no indications of lunule or escutcheon; hinge with 7 or 8 very 

 minute anterior and about 10 posterior teeth, the resilifer subumbonal 

 and minute. Length, 6; height, 4; diameter, 2.5 mm. Cat. No. 

 223578, U.S.N.M. 



Station 4224, in Boca de Quadra, Alaska, in 160 ^ tl^oms. mud. 



YOLDIA CECINELLA, new species. 



Shell minute, polished, smooth, nearly equilateral, the margins 

 arcuate above and below, the anterior end rounded, the posterior more 

 pointed and shghtly longer; beaks low and inconspicuous, with neither 

 lunule nor escutcheon indicated ; hinge with six or seven minute teeth 

 on each side of the subumbonal, very small resilifer. Length, 5; 

 height, 2.6; diameter, 1.5 mm. Cat. No. 211424, U.S.N.M. 



Station 2823, off La Paz, Gulf of Cahfornia, in about 26 fathoms. 



This species is quite close to Y. orcia, but is uniformly less acute 

 behind, smaller and more slender. 



