WORMS. TESTACEA. 66. Oltrea. 277 
Parafitica. Shell thin; lower-valve convex and thicker, the other flat. 
Rumpf. Muf. tab, 46. O. Klein Ofir. tab. 8. f. 17. 
Petiv, Amb. tab, 1g. fig. 11. 
Chemn. conch. 8. tab. 74. fig. 681. 
2. Adanf. Seneg.t. tab. 14. fig. 1. 
3. Clemn conch. 9. tab. 116. fig. 997. 
Inhabits the /ndian and At/antic feas, and fixes itfelf to the roots 
and ftumps of trees growing clofe to and hanging over the wa- 
' ter, efpecially the Mangifera; varies in form and fize, but is 
often as large as the palm of the hand. 
fixalbidas Shell thin, the upper-valve longer and more convex, 
Knorr Vergn, §. tab. 15. fig. 35 4- 
Inhabits the Adriatic, and is found fixed to other fhells fometimes 
alone fometimes feveral together ; about 1 £ inch long, but is 
variable as to fhape and fize; generally whitifh, rarely yellow 
pr violet, 
Crifata. Shell rugged, with imbricate lamelle: the margin with 
obtufely plaited teeth: the beak of one valve produced. 
Born. Muf. Caf. Vind. teft. Y. tab. 7. fig. 3. 
Inhabits Sbell an inch long and 10 lines broad, white with 
a few black fpots: Ainge with a broad conic tooth in the 
middle, 
Senegalenfis Shell equivalve roundifh fmooth flat. 
yt Adans feneg. i. tab. V4. ig. § 
Inhabits fhores of Sezega/, and adheres to rocks; about 2 inches 
in diameter: tawny, within whith. 
Sjellata, Shell thin depreffed rough unequal ; the upper-valve ribbed, 
QUE Ua the ribs with a few fpines. 
Schret. Einl. in Conch. 3. tab. 9. fig. 7. a. b. 
Inhabits Guinea, and is found affixed to other bodies by the 
hinge: fometimes round fometimes oblong ; very thin, white 
with red or blueifh rays fpots or marks. 
Ovahs. X Shell oval very thin and terminating in a fhort acute lateral 
channelled beak; with obfolete nnequal perpendicular 
{triz. 
Shret. Einl. in conch. 8. tab. 9. fig. 8. 
Inhabits Shell about an inch long, brittle, whitifh, within 
‘glofly filver-white : lower-valve exceeding the upper both in 
length and breadth. 
= 
Papyracea. Shell roundifh {nowy very thin pellucid; upper-valve ter- 
minating in a fhort acute beak. 
Schre, 
