Pvn H,i I'UitlS

386 TELLINID.E.
This large and well-known family differs from the
Venerida in the pallial tubes being invariably long and
separate, the beaks being less recurved, and the ligament
placed on the smaller side of the shell, and also in
having fewer cardinal teeth. The comparative length
of the tubes in each individual, caused by their exten-
sion or contraction, seems to depend on the will of the
animal; sometimes the incurrent, and at other times
the excurrent tube is the longer of the two. In families
which have these tubes united, there can, of course,
be no such inequality. Carpenter has shown that the
shells of the Tellinidce are of a solid texture, and that
their external and internal layers present appearances
of a prismatic cellular structure ; he termed these cells
" fusiform," and observed that they were arranged in
the two layers in opposite directions.
The Tellinida inhabit sand, and occasionally mud, at
all depths ;
some kinds are littoral.
Poli proposed the name Peronaea for the animals of
the genera comprised in the present family.
Genus I. GASTEA'NA *, Schumacher. PL VII. f. 2.
Body oval, tumid and thick : tubes having cirrous orifices.
Shell equivalve, inequilateral, wedge-shaped, ventricose,
decussated by concentric ridges or laminae and longitudinal
striae : teeth, one large cloven cardinal and a minute triangular
one by its side in the left valve, and two equal-sized divergent
cardinals in the right valve ; no laterals : inside margin
smooth.
The solitary species which represents this species in
the European fauna may be regarded by some as an
aberrant Tellina. The generic difference consists in
Gastrana having a more decidedly cuneiform and ven-
* So named from the turgidity of the shell.