NO. 1404. PARASITIC COPEPODS— C ALIO IBM- WILSON. 585 



(rlirnfi'j\ chrhi^ tli(> [)iMch(M--like claw of Crustacea, \u\(.\ fcro, to bear 

 or carry.) 



The National Museum collection when sent to the author contained 

 ))ut a single specimen, a female, of this species. It was numbered 

 (!o7U, and was obtained from the external surface of a menhaden at 

 Woods Hole hy the United States Fish Commission. The character- 

 istics of this specimen, especially the pincher-like claw, were so differ- 

 ent from other species that it was decided to make it the type of a 

 new species. Much to the author's gratitication he was fortunate 

 enough to obtain sev^eral living females from swordlish captured off' 

 Gay Head, Marthas Vineyard, in July, 1904. They were found on the 

 external surface in connection with C. rapax^ but were not nearly as 

 munerous as that species, only five being obtained from four swordtish. 



A single female taken from the cutlass tish {Trk-Jiiarus Icptiinix) on 

 September 16, 1903, by V. N. Edwards, was afterwards placed in the 

 author's possession. From the living specimens several facts were 

 ascertained, which have been incorporated in the previous description. 

 In addition it may ])e said that the species is almost as lively as rajxix, 

 swimming al)Out restlessly when kept in an aquarium. That it has 

 never been captured in the tow is pro])abh^ due to the fact that its 

 chief host, the swordtish, is an ott'-shore tish. So far as known this is 

 the only instance of a Caligus having anything which may fairlj^ be 

 called a chela. Many other species have protuberances of various 

 sorts on the inner margin of the basal joint of the second maxillipeds, 

 but they are simple protuberances and do not in any way extend out- 

 w'ard alongside the terminal claw and in opposition to it. Here, on 

 the contrary, it is to be noted that the conditions reproduce exactly 

 those in higher Crustacea. The outer, swollen branch of the chela is 

 articulated at its base, while the inner, larger ])ranch is inarticulate 

 and forms a part of the preceding joint. In place of the rounded 

 teeth so commonly found on this part of the chela we have here short 

 and stiff' spines. In the living specimens the chela was frequently 

 opened and closed, the tip of the claw, in the latter instance, folding 

 down over the end of the protuberance so tightly that the two seemed 

 all one piece. 



The comparative measurements of the menhaden and swordtish 

 specimens furnish a good object lesson on the shriid<age which results 

 from preservation in alcohol. 



One of the specimens was a female without egg-strings, and in this 

 condition the genital segment becomes so rounded anteriorly and pos- 

 teriorly as to be nearly a perfect circle in outline. The sp(>cies may 

 be easily recognized ])y the shape of the anal lamina^ and the length of 

 their plumose setse. An examination of the tips of the second maxil- 

 lipeds will then verify the diagnosis beyond a doubt. 



