256 REPORT ON ALBATROSS MOLLUSCA DALL. 



radiating sculpture of a ridge bounding the lunule over which the 

 lamellae pass, becoming finer and then obsolete toward the pouting car- 

 dinal margin; also, a ridge bounding the escutcheon, and a second less 

 obvious thread from the beak of each valve to the lower angle of the 

 rostrum ; the former shows by small elevated, pointed scales the influ- 

 ence of the lamellae, slight traces of which also appear on the second 

 ridge; the escutcheon is long, narrow, and smooth, with pouting lips, 

 and there are no developed lamellae between the ridges outside of it; 

 shell internally polished, showing no scars; there is no mesial ridge 

 in the rostrum ; cartilage large, black, triangular, posteriorly inclined, 

 wholly internal; teeth small, about forty anterior and fifty posterior to 

 the beaks, of which seven to nine on each side are undeveloped; on the 

 anterior side, between the anterior margin of the fossette and the tooth- 

 line proper, is a flat space over which these undeveloped teeth are 

 widened out as transverse, but little elevated, ridges; maximum longi- 

 tude of shell, 25.5; longitude from vertical of beaks to end of rostrum, 

 17; maximum altitude of shell, 8.75; diameter, 3.75 mm . 



Hab. — Station 2145, near Colon (Aspinwall), in 25 fathoms, mud. 



This is nearest L. concinna Adams, from Xew Zealand, but is propor- 

 tionally more elongated and pointed posteriorly, and more compressed. 



Leda platessa sp. uov. 



Shell thin, flat, smootb, whitish, nearly straight ; sculpture only of 

 faint incremental lines ; epidermis pale straw-color, translucent, pol- 

 ished; beaks small, bulbous, but inconspicuous, or hardly elevated 

 above the hinge-line; lunule so narrow as to be obsolete; escutcheon 

 extremely narrow, long, bordered by a faint thread, below which is a 

 still fainter one; base arcuate; anterior end eveuly rounded, short; 

 posterior end straight, squarely, not obliquely, rounded -truncate ; 

 interior polished, rostrum with a mesial septum most elevated distally, 

 nearly central ; fossette narrow, elongated, parallel with the cardinal 

 margin; teeth very small, anterior series with four undeveloped and 

 seven elevated teeth ; posterior series with about twenty-five developed 

 and eight or nine (?) undeveloped arched teeth; interior of shell pol- 

 ished, not showing the scars. Maximum longitude of shell 10.3 ; alti- 

 tude 4.4; diameter 2; vertical of the beaks from anterior end 3.25 mm . 



Hab. — Station 2762, east from Rio Janeiro, in 59 fathoms, mud; tem- 

 perature 57° F. 



The nearest relative of this shell is Leda Carpenter i Dall, from the 

 eastern coast of the United States and the Antilles. The latter has the 

 rostrum much more slender and more recurved, the lunule, and espe- 

 cially the escutcheon, wider and better defined, and the curve of the 

 anterior end more pointed in the middle. The central part of the base 

 below the beaks is also, in harmony with the general curvature of the 

 shell, proportionally more produced, The number of teeth on the 



