PARASITIC HABITS OF CRUSTACEA. 249 





























dread, serve to protect the crab, the latter can more effect- 
ually travel about and seek food, and while tearing its prey 
into small pieces, many choice bits doubtless fall to the lot 
of its companion. 
There is another group allied to the Hermits, the species 
of which often carry a valve of some bivalve shell upon the 
back for protection. At Florida and in the West Indies, 
Hypoconcha arcuata St., is found carrying a valve of Venus, 
or some similar shell, while at Panama H. Panamensis 
Smith* carries a valve of Pecten ventricosus, holding it on 
by means of the two posterior pair of legs, which are bent 
up over the back, aided by the posterior part of the body, 
which fits into the cavity below the hinge. An allied genus 
contains a species found from Florida to Brazil, Dromidia 
Antillensis, which carries upon its back, according to Dr. 
Stimpson, either a compound Ascidian or a Zoanthoid Polyp, 
. but all the specimens in the Museum of Yale College carry 
x à peculiar fleshy sponge, which fits upon and entirely covers 
the back, but is held in position by the four posterior legs. 
A peculiar genus of crabs, Dorippe, found on the coast of 
China, though not very nearly related to the two preceding, 
agrees with them in having the carapax broad and depressed, 
and in having the two posterior pairs of legs twisted up over 
the back, as if to hold on a bivalve shell, which may be 
their usual habit; but one of the species, D. facchino, was 
dredged at Hong Kong, carrying upon its back a beautiful 
Sea-anemone, Cancrisocia expansa St.,[ which completely 
Covers the back of the crab, and, like Adamsia, secretes 
from its base a thin, firm pellicle, to which it adheres, and 
by which the crab holds it in position with his four posterior 


OS MEN 
* Hypoconcha Panamensis Smith, sp. nov. Allied to H. arcuata Stimp. The carap 
howey. er, is narrower, the ualling the breadth; the anterior margin not £0 
id arcuate, and its edge broken by a marked median wn vnd 
eoiehes at the insertion of the antennæ; the projection in the anterior PAn e orion 

- * th enaces 




