SUPPLEMENT 
ON THE 
FIFTH CLASS OF THE MOLLUSCA. 
THE BRACHIOPODA. 
In the first genus of these bivalve mollusca, the animal has 
altogether the form of the shell; that is, it resembles pretty 
nearly a large claw, pointed at one extremity, widened at the 
other, which is nearly straight, with a short, obtuse, and 
middle point. The shell is moderately hollow, and is only 
curved in the direction of its breadth. It is formed, like all 
other shells, by imbricated strata from point to base. The 
two valves are not completely similar. The upper differs 
from the lower in having a sort of internal pad tolerably long 
and projecting, which corresponds to an excavation of the 
latter. At its base are two muscularimpressions. ‘The lower 
is a little larger, and more pointed behind. It gives an at- 
tachment to the tube, or ligament, in a small fossette, hollowed 
at its external face. 
The tube is very elastic, transparent, and striated trans- 
versely through its entire extent. It adheres to the lower 
valve by a thinner part. It is hollow in its entire length, and 
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