AT 
GASTROCH/ENA Spengler. 
Gen. Cuar. An inequilateral equivalved bivalve, 
with the anterior margin obliquely truncated 
and gaping ; the hinge-line straight, without 
a tooth, inclosed in a shelly sheath. 
Tue animal to which the shell above described belongs, 
perforates calcareous stones, corals or shells, by some 
solvent power, most probably not by wearing or scraping 
a hole, as Pholas and Teredo do; and lines the hollows 
more or less completely with shelly matter ; or it forms it- 
self a sheath of the same substance in sand or other loose 
or soft materials, some of which it unites to its fabric for 
its protection, as it is only in part covered by the two 
valves, which moreover are very slender. This sheath 
or case is commonly ovate, and of such a size and form — 
as to hold the valves easily, with the posterior part so 
produced into a tube as to contain the two united tubes 
of the animal, its extremity being flattened and partially 
