DALL: MOLLUSCA AND BRACHIOPODA. San 
not defined; anterior end evenly rounded, posterior more produced and attenuated 
but not acute; base evenly arcuate; surface with concentric riblets closely adja- 
cent, finer near the umbones, coarser and rounded near the base, extending over 
the whole surface except the upper posterior part, where they become obsolete ; 
interior polished, the scars hardly visible, the pallial sinus shallow; hinge with 
about eleven anterior and nine posterior, more or less folded teeth separated by a 
deep though small resiliary pit. Lon. 4.5; lon. of beaks behind the anterior end, 
2.0; alt. 2.7; diam. 1.5 mm. 
U.S. S. “Albatross,” station 3422, off Acapulco, Mexico, in 141 fathoms, 
mud, bottom temperature 539.5 F. U.S. N. Mus. 122,918. 
Easily distinguished from the preceding by its wrinkled surface and strongly 
recurved rostrum, and from the Leda cordyla group by its olivaceous instead of 
reddish brown periostracum. 
Leda (Leda) peruviana Da tt, nom. prov. 
Shell large, slender, rostrate, with a dark brown periostracum, the surface 
mostly smooth but with a few coarse irregular wrinkles on the basal half of the 
disk anteriorly ; with about fifteen anterior and thirty-eight posterior hinge teeth ; 
with a large obliquely posteriorly directed chondrophore, a short but strong longi- 
tudinal septum in the channel of the rostrum, and no perceptible vallial sinus. 
Lon. 22, anterior segment, 7; alt. 9.5; double diam. 6.0 mm. 
A single decayed valve was dredged in 1086 fathoms, mud, off Aguja Point, 
Peru, at station 4654. 
This resembles one of the pernula group of Arctic Ledas, but is clearly dis- 
tinct from any other, reported from the region under consideration. 
Spimula Datt, subg. nov. 
Shell rostrate, acute behind, smooth, with a well-developed short amphidetic 
ligament, an internal resilium supported by triangular chondrophores, a defined 
lunule and escutcheon ; a long, slender, completely united siphon, no palpal 
tentacles; pallial sinus obsolete. Type, Leda calcar Dall. 
The type of this group has a hinge and ligament so strong that it has been 
impossible to open a specimen without breaking the valves, and even then the 
hinge would not separate. The resilium is black, plainly visible from below 
within the shell. 
The animal has a long, contractile, slender siphonal tube, but there are no 
pallial muscles for retracting it, and apparently no marked sinuation of the pallial 
line. Mantle margin simple. Foot like that of Leda proper, the sole fringed 
and rather short. Gills short, palpi strong but without any accessory tentacles. 
The valves closed accurately. The adductor muscles seemed slender. The 
ligament is well developed and distinctly defined, short and about equally 
extended on each side of the beaks. 
