TO 1889. n '] PROCEEDINGS OF THE NATIONAL MUSEUM. 257 



hingediue is smaller, the fossette shorter and wider, and the rostral 

 septeui more dorsally situated. 



This species recalls, to some extent, Leda Bushiana Verrill, but that 

 species is more elevated and has sparse, prominent concentric lamellae 

 over part of its surface. 



Leda pontonia sp. nov. 



Plate xni, Fig. 5 b. 



Shell stout, strong, inflated, with a thin ochre-yellow or pale olive 

 epidermis and recurved, pointed, posterior end; beaks approximate, 

 full, incurved, not high, slightly anterior; anterior end evenly rounded, 

 produced; posterior end vertically compressed, produced, recurved, 

 pointed but not rostrate ; base evenly arcuate ; radiating sculpture of 

 occasional faint microscopic striatums near the ends of the shell, usually 

 absent, and a marked but not sharp-edged ridge in each valve, ex- 

 tending from the beak to the posterior point and bounding the pos- 

 terior dorsal area in each valve; concentric sculpture of numerous fine 

 regular continuous rounded threads, separated by narrower grooves ; 

 this sculpture, however, becomes suddenly obsolete on the cheeks of the 

 valves and in front of the ridges above mentioned; the threads are 

 stronger above and behind the ridges, but fade out in a central cordate 

 area which, though not impressed, may betaken to represent the escutch- 

 eon ; there is no obvious lunule ; interior polished, muscular and pallial 

 scars faint, the former small ; pallial sinus shallow, small, and terminal; 

 teeth V-shaped, anterior sixteen, posterior thirteen, all developed ; fos- 

 sette internal, deep set, subtriangular, short; maximum longitude of 

 shell 14.5 ; altitude 10; diameter 6.8 ; vertical of beaks behind the ante- 

 rior end 6.25 mm . 



Hab.— Stations 2807 and 2808, in 812 and 634 fathoms, mud and sand, 

 near the Galapagos Islands, Pacific Ocean ; temperatures 38°.4 and 

 40° F. 



This is a remarkably plain, stout, and simple species, notable for its 

 recurved tip, broad, flattened posterior dorsal area and arcuate base. It 

 has somewhat the form of L. chuva Gray, but is proportionally longer 

 and has a different sculpture. 



Family NUCULID^E. 



Genus NUCULA Lamarck. 



Nucula Verrillii Dall. 



Plate xiv, Fig. 4. 

 Nucula Verrillii Dall, Bull. Mus. Comp. Zool., xvm, p. 248, 1886. 

 Nucula trigona Verrill, Trans. Conn. Acad., vi, p. 438, 1885, notofBronn, 1849, or 

 Segueuza, 1877. 



Hab.— Off Nantucket at Station 2194 in 1,440 fathoms, and off the 

 coast of Maryland at Stations 2228 and 2229 in 1,582 and 1,423 fathoms 

 Froc. N. M. 89 17 



