CONCHOLOGICAL WRITINGS. 
4 
two eyes and no tentacula jutting out of the perforation. It would 
therefore deviate from the character of the family ; it may, probably, 
at a future period become the type of another; but the shell is so 
- very similar to Orbicula that I unite them now, proposing however 
for it a sub-family, under the name of Notremidia, which may 
become the family name when other similar genera shall have been 
detected. 
Description.—NotreMa. Generic character. Fluviatile bivalve 
shell, inequivalve ; upper valve larger, nearly round, perforated in 
the middle, opening -operculated: lower valve lateral very small 
inequilateral. Body flat beneath, head in the centre above, retracti- 
ble, jutting out through the perforation, with two lateral eyes, no 
tentacula. The generic name means opening in the back, in Greek. 
Notrema fissurella. Specific character. Upper valve convex 
with circular wrinkles, and oblique transverse furrows: lower valve 
flat. obovate and smooth ; shell fulvous brown, opening round, oper- 
culum round, brown, and shining, head truncate: ne 
Obs. It is found on the rocks of the bottom of the river Ohio, 
from the falls to the mouth; it is rare; diameter about one inch ; 
it holds on wrecks as the Patellas do, and might be mistaken for 
one at first; the operculum has a hinge, when the animal wants to 
protrude the head, it opens itas avalve. This shell might, perhaps, 
be deemed trivalve on that account. - 
C. S. RAFINESQUE. 
{From ‘Journal de Physique, de Chimie, d’Histoire Naturelle, etc.’ 
Tome LXXXVIII. Paris, June, 1819.] 
PRODROME 
De 70 nouveaux Genres d’Animaux découverts dans l’intérieur des 
Etats-Unis d’Amérique, durant année 1818 ; 
Par 0. S. RAFINESQUE, 
Professeur de Botanique et d’Histoire naturelle dans l'Université de Lex- 
ington en Kentucky. 
VI Classe. MOLLUSQUES. 
{[423] 
24. Puevurocera. (Spiral.) Coquille ovale ou pyramidale, plu- 
sieurs tours en aplomb. Ouverture oblique oblongue, base prolon- 
gée tordue, sommet aigu. lLévre extérieure mince, l’intérieure col- 
lée sur la columelle qui est lisse et tordue, sans ombilic. Animal a 
