600 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxthi. 



general details, but differ in several particulars, as also do the speci- 

 mens here described. The greatest differences are found in the f urea, 

 the first and fourth swimming legs, the abdomen, and the egg strings. 

 In Dana's original species the branches of the furca are longer and 

 more strongly curved, while in the present specimens the base of the 

 furca is larger and the branches are short, straight, and strongly 

 divergent. 



All the authors unite in characterizing the species by a complete 

 absence of the seta? on the posterior border of the first swimming legs. 

 In the present specimens the} r are certainly present, but are unusually 

 small. 



Dana's species shows the fourth legs three-jointed, with five spines, 

 all about the same length; in the present specimens there are but four 

 spines, and the inner terminal one is twice the size of the others. All 

 the authors write that the abdomen is obscurely two- jointed, but Kroyer 

 figures the adult female with an apparently one-jointed abdomen, as in 

 the figures herewith presented. Dana states that the egg strings are 

 "longer than the body" (p. 1354); Steenstrup and Liitken figure them 

 as onl} 7 half the length of the body, but as twice the length of the 

 abdomen, with eggs so large that each tube could contain only twenty. 



In the present specimens the egg tubes are but a trifle longer than 

 the abdomen (one-third the entire length), but each contains 40 eggs. 



In view of such differences it might seem as if the present specimens 

 constituted a new species, but after careful consideration this does not 

 seem to be warranted. In the first place, they come from the same 

 host as those obtained by the authors mentioned, a good presumption 

 in favor of their identity. 



Again, both Kroyer and Steenstrup and Liitken found great differ- 

 ences in their specimens, and they each figure what thev call a variety 

 of the species fully as different from the type as the present speci- 

 mens. Nor do the egg tubes here shown differ any more from those 

 given by the authorities just quoted than the latter do among them- 

 selves. For this reason these specimens have been referred to Dana's 

 species, and possibly the males reported by Brian (1898) niay belong- 

 here also. 



The foregoing are all the species of Caligus from North American 

 localities which are contained in the collection of the National Museum. 

 But in addition the following species have been reported from the 

 West Indies by various authors. The types of these species have 

 been lost or are contained in foreign museums. In most instances 

 the species are represented by very few specimens, sometimes onty 

 one or two, obtained many years ago, and none have since been found, 

 but this is chiefly, if not wholly, due to the fact that no investigations 

 have been made in that region since these specimens were found; 

 and there is every reason to believe that a careful search at the pres- 



