BOX- AND OYSTER-CRABS 287 
FAMILY CALAPPIDE 
Grenus Calappa 
C. flamma, the box-crab. This singular animal lives on sandy and 
muddy bottoms offshore, from North Carolina southward. The cara- 
pace is broad and straight on the posterior side, and is curved on the 
anterior side, narrowing to the front. The posterior side has promi- 
nent denticulations. The body is one and a half inches thick, about 
four to five inches wide, and two to three inches long. The chele are 
large, broad, and flattened, and are so arranged that when flexed they 
fit closely together across the front. When folded, and the small legs 
are withdrawn under the carapace, the animal is shut up as if in a box, 
and resembles a shell. When in danger it closes its doors, as it were, 
and abandons itself to the waves, which often carry it ashore. The 
crested claws resemble the head of a cock. (Plate LXIV.) 
FAMILY PINNOTHERIDE 
Genus Pinnotheres 
P, ostreum, the oyster-crab. The female of this species lives in the 
gill-cavity of the oyster, and is particularly abundant in oysters from 
the Chesapeake. The males are seldom seen, and rarely occur in the 
oyster, but swim freely about. They 
are smaller than the female, have a 
firmer shell, and are dark brown above, 
with a dorsal stripe andtwo conspicuous 
spots. The under side of the legs is 
whitish. The female is commensal, at 
least in the adult form, and its thin, 
wa fa aan cpp fe) bnged 
with pink. Thespecies P. maculatum ee one, 
lives a Mytilus edulis (mussel) and in the ze aden erste: Riese baa 
smooth scallop, Pecten magellanicus. The : 
oyster-crab is a true messmate, and its presence In the oyster may be ad- 
vantageous in helping to provide food for its host. This crab, like the rest, 
holds its eggs in the posterior feet until hatched, when the larve leave the 
parent and swim about fora while. The females, at the megalops stage, 
enter oysters — sometimes two enter the same oyster, but seldom more 
. than one; there it remains permanently, growing to the size of an inch 
or more in diameter, and becomes a degenerate. The eyes become 
smaller ; the shell never hardens, like its allies which live in open water ; 
its limbs and chele are weak; and it has no pugnacity, the protection 
afforded by the oyster doing away with the need for the common protec- 
tive features of its kind. Pinnixa cylindrica, a related species, lives in 
the tubes of large annelid worms as a commensal. 
