PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 401 



Leda unca Gould. 



Proc. Post. Soc. Nat. Hist., viii, p. 282, 1832.— Otia Conch., p. 239 (= f Leda 

 acuta Conrad, described as fossil). 



Many of our specimens are much larger than the shells described by 

 Gould and Conrad. Our larger specimens are 13'"" long, 8""" broad. 



This shell is rather strong and thick, oval, swollen, rounded anteriorly, 

 but posteriorly narrowed to an acute, short, angular beak, at the base of 

 which there is a slight incurvature of the ventral edge. The nearly 

 straight posterior dorsal edge slopes regularly to the beak, and is some- 

 what compressed or keeled. The whole surface is covered with numer- 

 ous prominent, regular, rounded, concentric ribs, separated by deep 

 grooves of about the same width. On the posterior dorsal area these 

 ribs are smaller, and are often nearly obsolete close to the edge. 



Taken in considerable numbers, alive and dead, at many of the sta- 

 tions, both south of Martha's Vineyard and south of Newi)ort, E. I., in 

 85 to 155 fathoms, especially at stations 871, 873, 874, and 870. 



This species appears to be allied to L. 3Iessanensis Cant. (= L. acumi- 

 nata Jeff.), from deep water in the Mediterranean. 



Leda pernula (Miiller). 



G. O. Sars, op. cit., p. 35, pi. 5, fig. 1 a-d. 



A specimen that appears to be a typical example of this speceies was 

 dredged by us in 1877, off' Halifax, in 59 fathoms. It has a smooth, 

 lustrous, yellowish- green epidermis. The concentric grooves are irreg- 

 ular and mostly obsolete, except anteriorly, where they are fine and 

 close. The form is similar to that of L. tenuisulcata. Length, 23'""' 3 

 height, 10'"'". 



Yoldia frigidia Torcll. 



Spitz. Moll., p. 148, pi. 1, fig. 3, 1859.— G. O. Sars, Moll. Ecg. Arct. Norv., p. 39, 

 pi. 4, figs. 11 a, b. 



This species occurred at station 894. It had not previously been ob- 

 tained off' tlie New England coast, but had been dredged in the Gulf of 

 Saint Lawrence, by Whiteaves, in 200 fathoms. 



Area glacialis Gray. 



G. O. Sars, op. cit., p. 43, pi. 4, figs. 1 a-c. — Verrill, Trans. Conn. Acad., v, 

 pi. 44, fig. 5. 



This species has been dredged in numerous localities by tlie various 

 dredging parties of the United States Fish Commission, since 1872, in 

 the Bay of Fundy, Gulf of Maine, off' Cape Cod, on George's and Le 

 Have Banks, and off Halifax, Nova Scotia, at various depths from 90 

 to 430 fathoms; about 70 to 75 miles soutli of jMartha's Vineyard, in 

 115 to 192 fathoms, and south of Newport, in 85 to 500 fathoms. It 

 attaches itself to pebbles or gravel-stones hj a small but strong ventral 

 byssus. 



The shorter and more rounded form, known as Area pectunculoides 

 Scacchi, also occurs on our coast, as well as the deformed variety called 

 var. septentrionalis by G. O. Sars. These appear to me to be mere vari- 

 Proc. Nat Mus. 80 26 Jan. 1 0, 1 8 8 1 . 



