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 amhulatory leg, right side 



The carcincecium 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 

 VerriU, 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 tbese polypean carcinoecia 

 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 polyp. In 

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

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

 In some cases the Adamsia has completely overgrown a small Epizoan- 

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

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

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

 usual in the species of Eupagurus, 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 disproportionau-ly 

 large for the crabs inhabiting them, having grown out 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 lega, as Spyropagurus spiriger has l>een observed to 

 do by Stimpson (Proc. Acad. Nat. Sci. Philadelphia, 1858, p. 248 (86), 1 - 



This specie was taken in great abundance, in 51 to 260 Fathoms, off Martha's 

 Vineyard, by the U. S. Fish Coinmittion, in 1880 ami 1881. 



