298 OSTREID. 
(exxxii, 8). Fossil, 46 sp. L. Oolite—Chalk; United States, 
Europe. 
ALECTRYONIA, Fischer de Waldheim, 1825. (Lopha, Bolten, 
1798. Dendostrea, Swainson, 1840. Actinostrea, Bayle.) Shell 
plicate, strongly so towards the margins ; adherent partly by 
recurved spinous processes clasping the limbs or roots of trees, 
as mangroves, ete. O. frons, Linn. (exxxi, 79). 
GRYPHHA, Lamarck, 1801. (Pyenodonta, Fischer, 1835.) 
Shell free or very slightly attached ; left valve with a prominent 
incurved umbo; right valve small, concave. Fossil, 30 sp. 
Liassic—Cretaceous; Eur., India, U. S.  O. angulata, Lam. 
(cxxxii, 4). 
GRYPHOSTREA, Conrad, MSS. Shell thin, elongate, straight, 
narrow ; lower valve rather deep and smooth; upper valve flat 
or slightly concave, and ornamented with distant, regular, thin, 
concentric lamin; beak of lower valve contorted, or turned to 
one side; cartilage-pit narrow, oblique. In perfectly preserved 
specimens the typical species, O. vomer, throws out long, slender 
auricular appendages (one on each side) from the lower valve 
near the beak. They are usually broken off, but appear to have 
attached the species. 
