176 BULLETIN 97, UNITED STATES NATIONAL MUSEUM. 



Description of male. Firmer than female and of smaller size; 

 fronto-orbital width nearly half of carapace width; chelae shorter, 

 margins of palm convex; fingers more horizontal. Legs more un- 

 equal, the fourth definitely the smallest, the first stoutest ; propodites 

 faintly curved, dactyli longer than in female, third longest. Abdo- 

 men tapering regularly from third to sixth segment, the latter con- 

 stricted at middle ; terminal segment with end rounded. 



Measurements. Female (49238), length of carapace 13.2, width of 

 same 15 mm. Male (22112), length of carapace 7, width of same 

 7.6 mm. 



Habitat. Parasitic in sea-urchins (C ' aenocentrotus gibbosus and 

 Loxechinus albus]. Nearly all the specimens of C. gibbosus in the 



FlG. 111. PlNNAXODES CHILENSIS, MALE "(221 12 ). O, ENDOGNATH OF OUTER MAXILLIPED, 



MUCH ENLARGED ; ft, ABDOMEN, X 4|. 



United States National Museum show evidence of parasitization. 

 Verrill says * of a collection of 90 specimens of this urchin : 



An examination of the interior showed that in each specimen a crab (Fabia 

 chilensis) * * * had effected a lodgment in the upper part of the intes- 

 tine, which had thereby been greatly distended in the form of a membranous 

 cyst, attached to one side of the shell and extending around to the lower sur- 

 face near the mouth. The shell is usually swollen on the side over the cyst, 

 and the anal area is depressed and distorted, with a large open orifice passing 

 obliquely into the cyst, out of which the crab may thrust its legs at pleasure, 

 but is apparently unable, when full grown, to come entirely out. All the speci- 

 mens examined in the cyst were females, carrying eggs, but a very small crab 

 found clinging among the spines appears to be the male. The crab probably 

 effects an entrance into the intestine through the anus while quite young, and, 

 by its presence and growth in that position, causes the gradual distortion of 

 the shell and formation of the cyst.* 



Range. Ecuador to Port Otway, Patagonia. 



1 Amer. Jour. Scl., ser. 2, vol. 44, 1867, p. 126. 



2 For further notes on the habits of this species, see Verrill, in Trans. Connecticut Acad. 

 Arts and Sci., vol. 1, 1866, p. 306, and Amer. Nat., vol. 3, 1869, p. 246. 



