AMPHIPODA OF SOUTHERN NEW ENGLAND. 



513 



were examined, while in our species they are composed of bul two. The large hands of the males are 

 much alike in the two species, but are somewhat narrower and with a more slender dactyl and basal 

 process in pulch* Ua. 



There is an apparent dimorphism among the males of this species, similar to that which is said to 

 occur in European species of the same genus. The different forms of the males of Jassa pulcheUa have 

 been regarded by Boeck and Hoek as due to age. Nebeski, however, dues not share this view, since 

 he rinds that the two forms of the male are often of equal size. An examination of quite a large 

 number of males of marmorata of different ages shows that the changes in form of the large chelipeds 

 are correlated with different stages of growth. In the small males the hands resemble those of the 

 females. In the largest males the hand is elongated, as shown in the figure, and furnish, d with a long 

 basal projection. Among males of intermediate size this projection is of variable length, but never so 

 large as in the largest specimens. The fact that the two types of hand are found in individuals of 

 about equal size may be accounted for on the supposition that the one form is younger than the other 

 and has not passed through the requisite number of molts to attain the final form, but has grown 

 more rapidly. The rate of growth depends largely on food supply, which may vary considerably in 

 different situations. One individual might easily attain the size of another without having passed 

 through so many periods of molting. 



Ischyrocerus anguipes Kroyer. 



Cerapus fuckola Stimpson, Marine Invert. Grand Manan, p. 4s, tig. 34, 1853. 

 Podocerus/tu-icola Smith, Rept. U. S. Fish Coin. 1871-72, p. 566. 



Male: Eyes nearly round; first antenna- considerably shorter than second; second joint of pedun- 

 cle a little louger than third and nearly twice as long as first; flagellum shorter than last two joints of 



0r» \ 



Ischyrocerut anguipcs. Marblebead Beach, Mass. 



peduncle; secondary flagellum very small, consisting of an elongate joint and a minute terminal joint; 

 second antenna' stout and elongate, last two joints of peduncle of subequal length; flagellum shorter 

 than last joint of peduncle, and composed of five or six joints, of which the first is longest; terminal 

 joints with curved spines; first four coxa] plates subquadrate, about as deep as long and as high as 

 their respective segments; first gnathopods small, basal joint broad; carpus rounded and setose 

 behind; hand subovate, palm very oblique and nearly straight, a row of four or five seines beginning 

 near end of palm and extending along posterior margin of hand, finger with inner margin acutely 

 serrate; second gnathopods large, much elongated, basal joint narrow, elongate, gradually widening 

 distally and curved forward, lower anterior angle produced downward into a rounded lobe; ischium 



