■imi 
PALEONTOLOGY OF NEW-YORK. 
slightly outwards, send off a short spur into the ventral cavity and are 
thence directed forwards, and gently curving, join the median crest, to 
which they are attached, forming a loop of peculiar character. The occlu- 
sor muscular impressions have rarely been seen with any degree of dis¬ 
tinctness ; hut the depressions just at the termination of the crural 
processes, and on each side of the median ridge, are striated; and this 
striation often extends in a wide flabelliform expansion, probably due 
to vascular impressions. Towards the margin, the interior of both valves 
is strongly pustulose. 
The accompanying wood-cuts illustrate the parts referred to above. 
Fig. l. 
Interior of the dorsal valve. 
b. Crenulated teeth-sockets. 
c. Crural processes. 
1. Loop.. 
s. Septum. 
Fig. 2. 
Longitudinal section of the dorsal valve 
j. Cardinal process. 
b. Tooth-socket. 
c. Crural processes. 
1. Loop. 
s. Septum. 
In the punctate texture of this shell, it differs from either of the Genera Lep- 
xasNA, Strophomena or Strophodonta ; but this might not be an objection to 
admitting Tropidoleptus into the family, were the other characters coincident. 
The area is longitudinally striated, and presents a different aspect from any of 
the Strophomenidad , but has analogy with some of the Orthides. The teeth are 
not extensions of the lamellae bounding the foramen, but distinct from it and 
deeply crcnulate or lobed, and inserted into corresponding crenulate sockets in 
the dorsal valve. The form of muscular impressions, so far as known, is not very 
dissimilar to those of Strophomena or Orthis. 
In comparing the form of the cardinal process and its appendages, we shall 
find it almost entirely similar to that of Leptoccelia, as shown in two authentic 
species (L. flabellites and L.Jimbriata), and the muscular impression of the ven¬ 
tral valve is quite like that of the same species. 
