PELECYPODS 441 
tropical genera as Voluta and Conus are found fossil in northern 
Siberia seems to be evidence in proof of great climatic variations. 
A. castanea. This species has a thick and heavy shell for one so 
small, with round ventral margins and prominent beaks. The surface 
is very slightly undulated and is covered with a thick 
chestnut epidermis with pale and dark zones. The 
hinge is broad and flat, with a prominent cardinal 
tooth upon the right valve, which accurately fits into 
a pit formed by two teeth on the left valve. Length 
= one inch; height one inch. 
A. undata. A species slightly larger 
than the last, with ten to twenty promi- 
nent concentric undulations. 
The identification of the many species 
of Astarte often becomes exceedingly difficult on account 
of the fact that the genus is a remarkably uniform one in 
its main characters and is infinitely variable in its minor details. 
Astarte castanea. 
Astarte undata. 
FAMILY CYPRINIDE 
Genus Arctica 
This family is represented by one species upon the New Eng- 
land coast, which is much ‘sought after by collectors. It is one 
of the larger clams, 
but is too uncommon 
to have received a 
popular name and to 
be generally well 
known by the fisher- 
men along the shore. 
A. (Cyprina )istan- 
dica. This clam has a 
thick though not pon- 
derous shell, with promi- 
nent beaks and a stout, 
prominent ligament. 
Its cardinal teeth are 
large, but its laterals are 
very small. A striking 
feature of this species, 
which at once separates Arctica (Cyprina) islandica. 
