103 
OSTREA, 
Gen. Char. A rugged inequivalved bivalve; hinge 
without teeth; pit of the hinge transversely 
* striated*; increasing with age (or commonly 
broader inwards) ; cartilage half internal. One 
muscular impression in each valve. 
OSTREA Marshii. 
TAB. XLVIIL 
Spec. Char. Oblique, both valves deeply plaited in 
seven or eight angular diverging undulations ; 
edge thicks flatted. 
This is a strong depressed shell very variable in form, 
though generally longer than wide, and often furnished 
with an obscure ear upon the posterior side. There is such 
variety among the recent individuals of the Oyster tribe, 
that it is one of the most difficult tasks in Conchology to 
distinguish the species, much more so when we add the 
fossil and otherwise antient j*emains, which, however, are 
seldom replaced but by a siliceous infiltration between the 
laminae becoming, Calcedony, &c. 
The present species, nevertheless, from its first appear- 
ance, seems to claim a place as perfectly distinct from the 
* Tripartite, central division generally broadest, to which the cartilage 
is attached. 
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