170 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 50 



Genus NUCULA Lamarck 

 NUCULA MIRIFICA Dall, n. sp. 



Shell olive brown, with a brilliantly polished periostracum, ob- 

 scurely microscopically radially striate or smooth, with faint concen- 

 tric incremental irregularities ; beaks low and inconspicuous, pro- 

 soccelous, very anterior ; general outline egg-shaped, the short an- 

 terior end obscurely truncate, lunnle and escutcheon absent, though 

 there is a slight depression under the beaks without definite limits ; 

 interior nacreous white, the margins entire, pallial line and muscular 

 impressions distinct but not deep ; hinge line evenly arcuate, divided 

 by a large, obliquely directed chondrophore ; teeth of the anterior 

 series crowded, 10 to n in number; posterior series with 16 to 17 

 less crowded prominent teeth. Alt., 26; Ion., 36; diam., 16 mm., 

 the vertical of the beaks 6 mm. behind the anterior extremity of the 

 valves. 



U. S. S. Albatross, station 5040, south coast of Yesso, October 3, 

 1906, in 269 fathoms. U. S. Nat. Mus., 110,463. 



This appears to be the largest smooth and typical Nucula yet de- 

 scribed, though a specimen of Acila mirabilis Adams and Reeve, 

 was obtained at station 4994, in 190 fathoms, which measured 41 

 mm. long, 29 mm. high, and 22 mm. in diameter. 



Genus PECTEN Muller 

 PECTEN (CHLAMYS) ERYTHROCOMATUS Dall, n. sp. 



Shell resembling P. hcriccus Gould and P. islandicus Muller in 

 general appearance, but differing in the following details. Than 

 islandicus it is somewhat more rounded in the disk and more con- 

 vex; the anterior ears are smaller and more vertically truncate dis- 

 tally ; the hinge line is shorter and the posterior ears smaller and the 

 byssal fasciole narrower ; the radii are smaller, keeled and minutely 

 spinose instead of smooth and flat on top and laterally rounded; 

 the minor reticular sculpture is more oblique and rough, the chan- 

 nels between the radii relatively wider ; the radii themselves are gath- 

 ered obscurely into fascicular bundles, which as a whole are raised 

 like wide obsolete ribs ; the colors are obscurely radial, rose-red and 

 white instead of mainly concentrically distributed. Than h eric ens 

 the hinge-line is more horizontal and the anterior ears much smaller, 

 the byssal fasciole much narrower, the minor sculpture more rasp- 

 like, the individual spinules straight distally instead of arcuate, the 

 larger riblike fasciculi very much less distinct, only five or six in 



