THE NAUTILUS. 33 
the pallial sinus deep, reaching more than half way from the verti- 
cal of the beaks to the anterior adductor; one bifid cardinal tooth 
in the left and two in the right valve, without laterals; ligament 
short, strong ; exterior with nearly smooth beaks and no radiating 
lines, but most of the valve covered with low elevated concentric ir- 
regularly broken lines, which are irregularly swollen or granulose 
minutely in a longitudinal sense ; color of the shell pale lemon-yel- 
low or white, without distinct epidermis. Alt. 6:0, lon. 13°0, poste- 
rior end 6:0, diam. 3°5 mm. 
Gulf of Mexico west of Florida in 26 fathoms ; off Cape Lookout, 
N. Carolina, in 22 fathoms; Barbados in 100 fathoms. 
This curious shell is distinguishable from any other American 
species by its peculiar surface. It grows twice as large as the meas- 
urements given above. 
Macoma Mitchelli, n. s. 
Shell small, thin, polished, pinkish-white, moderately inflated ; 
teeth as in M. limula but more feeble; valves closely resembling 
Tellina versicolor Cozzens, but without the lateral teeth, less solid, 
the pallial sinus more distant from the anterior adductor, the pos- 
terior dorsal slope less arched and not quite so long, the muscular 
impressions less impressed and the anterior end somewhat broader ; 
in M. mitchelli the surface is mostly smooth, but near the ventral 
margin, especially in front, there are impressed, somewhat distant 
and inconstant, concentric lines in harmony with the lines of growth 
or nearly so. Alt. 8:25, long. 15:0, post. end 6°0, diam. 4:0 mm. 
Habitat, Matagorda Bay, Texas, (I. D. Mitchell). 
Macoma leptonoidea, n. s. 
Shell very thin, high, short, polished, smooth or with fine silky 
concentric striule under a thin iridescent epidermis; hinge very 
feeble, teeth as in M. limula; pallial sinus irregular, reaching about 
two-thirds the whole length, backward from the front edge of the 
valves; outline of valves leptonoid, the anterior slope longer and 
more rounded, the posterior shorter and more direct but not ros- 
trate, though there are two obscure ridges radiant backward from 
the beaks but not modifying the posterior margin ; the shell is some- 
what compressed but not flattened. Alt. 13-0, lon. 16, lon. of post. 
end 6:0 diam.6°0 mm. Matagorda Bay, Texas, (Lloyd.). 
This little shell looks curiously like a Lepton. Its outline, though 
larger, differs little from that of Lepton longipes Stm. The types of 
