“We have now finished our first division, and


must proceed to the bivalves.”


MYA. Z|


CHAPTER, 1y-


Sreconp Division.—Bivalves: 14 genera.
‘¢ | rear,” said Charles, “ that this new division
will be rather difficult, for my father tells me that
we must pay particular attention to the hinges of
bivalve shells.”

‘* Then apply yourself to the study of hinges,
Charles, and your difficulties will chiefly disap-
pear,” answered Mr. Elliot.
‘* The hinge of Mya, the first on the list, is
easily known. The generic characters are, shell
gaping at one end, hinge mostly with one thick
spreading tooth, not inserted into the opposite
valve. The Mya race burrow in the sand. Here
is Mya arenaria, a large thick shell, frequent
on the shores of Kent: the large tooth is suffi-
ciently plain in ¢his species. Mya truncata
(PLATE 4) is as common, and the curious mem-
branous case, which you will find attached to one
end of the shell, is a guide to the species. Both
these species are without colour, and have little to
attract in their outward appearance. The genus,


92 SOLEN. TELLINA.
however, according to Linneeus, varies exceed-
ingly, and contains forty-one species.
“« Solen. Shell bivalve, open at both ends,
tooth of the hinge subulate, or awl-shaped, reflex,
often double.
‘* In this genus, the great length, in comparison
with the breadth of the shells in many of the
species, is remarkable: some are exceedingly
brittle. Our example, Solen siliqua (PiatE 1)
is a British species. The hinge is not in the
centre of the shell, but nearer to one end of it.
Some are shaped like the handle of aknifeor a razor,
others are bent resembling the blade of a scimitar.
