)S. 1. Smith on American Crustacea. 171 



The parasitic liabits of this species have been fully described by- 

 Prof. Verrill.* It inhabits JEuryechinus imhecillis Verrill, living in a 

 sac formed by the distention of the intestine near the anal orifice. 

 The females, after they have arrived at any considerable size, must 

 remain permanently within the same echinus, since the anal orifice is 

 much smaller than the body of the crab. 



I have examined quite a number of individuals obtained from spe- 

 cimens of the Eiiryechinus collected by Mr. Bradley at Paita and 

 Callao, Peru, and by Prof. James Orton at Paita, and have little 

 doubt that the species figured by Edwards and Lucas and by Heller 

 ai-e identical, although the figui-es given by these authors are quite 

 different. The specimens l^efore me agree very well witli the figure 

 in the work of Edwards and Lucas, except that the outer margin of 

 the carpus of the external maxillipeds is not quite so much curved 

 toward the distal extremity as in the figure. On account of the soft 

 and yielding nature of the carapax, many of the specimens do not 

 show distinctly the sulci in the dorsal surface. The figure given by 

 Heller seems to have been drawn from such a specimen, for no sulci 

 are represented. The carpus in the figure of the external maxilliped 

 in Heller's work, is quite different from Edwards' and Lucas' figure ; 

 but the figure of the latter authors represents the whole maxilliped 

 removed from the rest of the animal, while Heller's figure represents 

 only the exposed portion, and Avas evidently drawn from the maxilli- 

 ped while in place, and, if the carpus were seen in a slightly oblique 

 position, it would account for its narrower Ibrm in his figure. The 

 dactyli of the ambulatory legs, as represented in Heller's figure, are 

 somewhat longer than in oixr specimens. 



The peculiar habit is also a confirmation of the identity of the spe- 

 cies. Heller's specimens were from Ecuador, and he says of them : — 

 " Diese in zwei weiblichen Examplaren vorliegende Art soil nach Dr. 

 Scherzer in einer Echinus-Art vorkommen." Neither Edwards nor 

 Edwards and Lucas give anything in regard to the habits of the spe- 

 cies, but merely state that it was found at Valparaiso. Dana, how- 

 ever, mentions it as " from an Echinus on the coast of Chili, near Val- 

 paraiso." 



A single specimen of a male, which evidently belongs to this spe- 

 cies, was found upon the outside of an echinus which contained within 

 it a female. This male is very small, the carapax is rather narrower 



* These Transactions, vol. i, p. 306, American Journal of Science, 2d series, vol xliv, 

 p. 126, 1867, and American Naturalist, vol. iii, p. 245, 1869. 



