CONCHIFERA. 
4o9 
nearly flat, the other convex; rounded at the anterior end. One 
inch broad. Inhabits the Mediterranean and British seas. 
Genus 46. — CORB ULA.— Bruguiere. 
Generic Character. —Shell regular, inequivalve, inequilateral; 
with a conical, bent, ascending, primary tooth in each valve •, a 
small pit at its side; destitute of lateral teeth; ligament ex¬ 
ternal. 
Corhula nucleus .— The Kernel Corbula. 
Plate XC. fig. 20. 
Somewhat triangular, strong, with the under valve much 
larger than the upper one; transversely striated ; covered with 
a thick, brown epidermis. Half an inch long. Inhabits the 
British seas. 
TRIBE IV.-MACTRACiEA. 
Equivalve shells, frequently gaping at the lateral extremities; 
with an internal ligament, or partly external, and the animal 
having a small compressed foot. 
* Ligament seen externally or double. 
Genus 47.—AMPHIDESMA. — Lamarck. 
Generic Character. —Inequilateral, transverse, suboval or 
somewhat rounded ; with sides slightly gaping ; hinge with one 
or two cardinal teeth, and a narrow groove for the internal liga¬ 
ment ; ligament double, the external one short, the internal one 
flxed in the internal grooves. 
Amphidesma reticulata. —The Reticulated Amphidesma. 
Plate XC. fig. 24. 
Sub-orbicular, sub-diaphanous, compressed, finely reticulat¬ 
ed ; yellowish-white. One inch and a quarter long. Inhabits 
the West Indian seas. 
Genus 48.— SOLEMYA— Lamarck. 
Generic Character. —Inequilateral, equivalve, transversely 
elongated, extremities obtuse, with the epidermis smooth, shin¬ 
ing, and projecting ; beaks not prominent and hardly distinct ; 
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