
246 PARASITIC HABITS OF CRUSTACEA. 
parasitic in the shell of Tridacna, of the East Indies, and in 
the large Pinna of South Carolina. Another genus, Pinnixia, 
allied to Pinnotheres, has two Carolina species. P. cylin- 
drica Say,lives in the tubular burrow of a large worm, 
Arenjcola cristata; the other, P. Cheetopterana St., lives 
in the strong tube of another large worm, Cheetopterus per- 
| gamentaceus St. Another allied form, remarkable for its 
nearly globose body and hairy legs, Pinnaxodes Chilensis 
Smith (Fabia Chilensis Dana), lives upon the coast of Peru 
and Chili in the shell of a small species of Sea-urchin (.Zu- 
ryechinus imbecillis Verrill), which it causes to grow out of 
shape. It appears to enter the anal opening when quite 
small, and retaining its position until fully grown, causes 
the intestine to dilate into a sort of cyst, and the anal area 
and upper part of the shell to become deformed. When 
fully grown it often fills nearly a third of the body of its 
host, and yet has but a small external orifice, out of which 
it probably cannot come, but the male, being much smaller, 
may readily enter. From the fact that nearly all the speci- 
mens of this Sea-urchin found thrown upon the beach, 
amounting to over one hundred, had this parasite, it is prob- 
able that it eventually weakens or kills its host by the irrita- 
tion it produces. 
Another very singular genus, Harpalocarcinus marsupi- 
alis St., lives among the branches of Pocillipora ccespitosa, 
at the Hawaiian Islands, and by its constant motions while 
remaining in one spot causes the coral to grow up around 
itself so as to form as perfect and secure a residence as could 
be desired, while openings are left to admit water and food. 
I have observed similar cavities on Pocillipora elongata 

“ashton small, about half as long as the carpus; legs of the second pair stout, the 
hands somewhat unequal ana much than the carapax, much swollen, fingers 
compressed, their inner edges sharp, the dactylus — and with a rud tooth in 
ng legs 

2d propodus; succeedi 
ede qut cylindrical, the dactyli very short and perdon ehsa , the terminal pis 
culus strongly curved, and a shorter one very much hooked at its base. Abdomen 
Small the first six segments slightly exceeding in length the length of the carapax. 

GI c p M ne Ses 

D D MEUM MS M E CEA Rc c Un E s ae pedea dip a umi ecu terum 

