SI LITE ! AN 
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loping the deeply-concave dorsal valve. Both valves conspi¬ 
cuously radiated by distant ribs, connected by fine transverse 
lines. The valves are largely undulated lengthwise, and 
minutely corrugate along the hinge line for some distance on 
each side the beak. Ventral valve generally convex, with a 
raised central fold and some lateral fainter undulations, the 
stronger ribs, about twenty, with shorter intermediate ones ; 
all distinct and thread-like, without intervening stria3, but 
crossed by numerous very fine web-like concentric lines and 
some conspicuous ridges of growth. Beaks not at all pro¬ 
minent. 
The involute habit of this really beautiful shell is very much 
that of a Leptceena. The corrugations,however, along the hinge 
border, betray its real affinity, which its expanded form con¬ 
firms. I have not seen the interior. 
Locality .—Damchen (1678). Chorlioti Pass (1737, 1752): 
Milam Glacier (Nos. 932-3). 
STROPHOMENA ARANEA. 
Plate 3, fig. 10. 
L. uncialis et ultra, semiovalis, angulis rectis, paucicostata, costis 
remotis; valva ventrali convexa, altera plana. Valva major regulari- 
ter convexiuseula, nate minima vix elevata ; dorsalis plana, vix concava, 
crassa, intus cicatricibus, dentibus, septo longo, sulcoque concentrico 
rugosa. Costulae rectse, baud striis interlineatse, remotae, rete concen¬ 
trico conferto connexae. 
Width fourteen or fifteen lines, length eleven lines. Semi¬ 
oval, one valve (ventral) convex, the other flat or slightly 
concave, conspicuously radiated with distant fine ribs. Hinge 
line equal to the width of the shell, the ears not projecting. 
Dorsal valve very flat, and marked by remote and not very 
prominent ridges, on a flat surface, crossed by strong concen¬ 
tric striae as conspicuous as the ribs. In the other valve the 
ribs are interlined by shorter intermediate ones. 
Interior of the dorsal valve with strong teeth, the outer 
ones widely divergent, and with well-marked muscular im¬ 
pressions—the latter covering a circular space, which stretches 
