CONCHOLOGICAL WRITINGS. 87 
14 G. OrprcuLa (Cuvier, Lamark.) Shell orbicular, one valve flat 
and one conical. 
15 G. Strophesia, Raf. Shell orbicular equilateral, beak curved 
in the great valve. 
16 G. Diclipsites Raf. Differs from last by hinge short and 
straight ; no proeminent beak. 
17 G. Truncurites, Raf. Subequital, valves convex, equilateral, 
nearly equal, hinge short and truncate. 
18 G. Productus, (Sowerby,) Equilateral, winged, or rather 
auriculated, one valve convex, the other flat or convex, hinge 
linear. 
19 G. Styriasis, Raf. Differ from last by great valve, with a pro- 
jecting cruciform appendage on the beak. 
20 G. Goniclis, Raf. Shell longitudinal, great ae concave 
inside, with a longitudinal angle outside. 
21 G. Megarites, Raf. Shell longitudinal, equilateral suborbicular, 
valves nearly equal, both convex with concentric ridges, hinge like 
a linear horizontal fissure. 2 
Most of the species belong to the following Genera. 
Obovites—6 sp. 
Gonotrema—15 sp. 
Platilites—13 sp. 
‘ Shophomenes—16 sp. 
In a supplement of March 1821, I added 2 N. G. 
22 G. Amblotrema, Raf. Differs from Gonotrema by the opening 
or perforation, being oval or oblong, and obtuse. 
23 G. Pleuranisis, Raf. Differ from Platilites by having the 
shell inequilateral. 
The geological age of these shells appears the same as that of 
the oldest fossils, Madreporites, Turbinolites, Encrinites, &c., being 
found together and promiscuously in the same strata, or in diluvial 
debris ; but the different genera and species are not found together, 
sometimes they are wide apart, or very rare; they are mostly 
silicified. 
