18 BULLETIN OF THE 



Greatest diameter of eye 



Length of right cheliped ... . . 



" chela 



Breadth of propodus 



Length of left cheliped 



" chela 



Breadth of propodus 



Length of first ambulatory leg, right side 



The carcinoecium is very rarely a naked gastropod shell ; in most of the 

 specimens seen it is either built up by a colony of Epizoanthus Americanus, or 

 is made up in a somewhat similar way by the single polyp of Adamsia sociabilis 

 Verrill, the base secreted by the Adamsia being expanded on either side and 

 united below so as to enclose the crab in a broadly conical cavity, with only a 

 slight spiral curvature. The nuclei about which these polypean carcincEcia 

 are formed are of various origins ; the majority of the Adamsia carcinoecia 

 appear to have been built upon fragments of pteropod shells, in some cases 

 upon bits of worm-tubes, in one case upon the entire shell of a Cadulus, the 

 greater part of the shell being left protruding from the base of the polj^p. In 

 the carcinoecia formed by Eiyizoanthus the nucleus seems usually to have been 

 absorbed, so that nothing is left distinguishable from the colony of polyps 

 itself. In some cases the Adamsia has completely overgrown a small Einzoan- 

 thus carcinoecium, so that when the Adamsia is removed a perfect Epizoanthus 

 carcinoecium is found beneath as a nucleus. The carcinoecium of this species, 

 and of C. gracilis as well, does not cover the animal to the same extent as is 

 usual in the species ofEupagurus, the anterior part of the carapax being appar- 

 ently constantly exposed, and its induration fitting the animal for such expos- 

 ure. The Epizoanthus carcinoecia are, however, very often disproportionately 

 large for the crabs inhabiting them, having grown put either side until they 

 are several times broader than long. In spite of these often enormous carci- 

 noecia, both species of the genus probably swim about by means of the ciliated 

 dactyli of the ambulatory legs, as Spiropagurus spiriger has been observed to 

 do by Stimpson (Proc. Acad. Nat. Sci. Philadelphia, 1858, p. 248 (86), 1859). 



This species was taken in great abundance, in 51 to 250 fathoms, off Martha's 

 Vineyard, by the U. S. Fish Commission, in 1880 and 1881. 



