119 
EAST. ZOOL. GAL.] NATURAL HISTORY. 
cuIce in shape, and having a thin margin, the pits project 
into the cavity, or in Verna , which are like the Mallei or 
Hammer Oysters in form, but having a very thick hinge 
margin, forming an area on the top of each valve, the car¬ 
tilage pit forms distinct grooves across it. Besides these 
there are numerous fossil genera, as Inoceramus , Pachy- 
mya , Gervillia , which must be referred to this family; the 
latter is peculiar for having teeth like Avicula, but more 
developed, as well as the many cartilage pits of Crenatula , 
The Micropoda have a large single adductor muscle, 
placed nearly in the centre of the sub-orbicular shell. 
The mantle-lobes are always entirely free, except near 
the dorsal edge, and without any peculiar tubes; they ge¬ 
nerally have only the rudiment of a foot on the lower side 
of the abdomen, and sometimes no apparent one. 
In some the shells are solid, thick, and the animal has 
a more or less developed foot; the cartilage is placed 
in a small triangular internal pit. 
The family of Pectinidce have a moderate sized hatchet¬ 
shaped foot, which enables the animal to move about, and 
they have a tuft of byssus at its base, which passes out at 
a notch under the front margin of the right valve, by 
which they affix themselves to rocks and other marine 
bodies, like the Muscles. The dorsal edges of the valves 
are produced at each side into ears. The Pectens have 
small bright eyes like spots on the edge of the mantle, 
which are not found in the Limce. 
The family of Spondylidce have a small foot without any 
byssus, and the shells are attached to rocks and stones 
by the outer surface of one of the valves. In Spon- 
dylus and Plicatula , the hinge margin is provided with 
two large interlocking teeth in each valve, and in Hinnites 
the hinge is toothless like the Pectens , with which it has 
generally been confounded. 
The animals of the remaining families, have lamellar 
shells and no foot. 
The family of Oysters ( Ostreidce ) have a thick laminal 
shell, and the animal has short lips, separate from the 
gills ; they live attached, like the Spondyli , by the outer 
surface of their shells; the cartilage is placed in a large 
triangular internal pit. 
The family of Placunidce are very peculiar for having 
