NO. 1504. AMERICAN PARASITIC COPEPODS— WILSON. 703 



It is very apparent from an examination of Kroyer's figures and 

 description that liis "male" was simpl}- a female without egg-string-s, 

 while Bassett-Smith's was a female with egg-strings. 



Any attempt, therefore, at sex differentiation between the two is 

 futile. The new species here described with their entire life history, 

 and the true males now for the first time completely differentiated, 

 necessitate many changes in both these generic diagnoses, that of 

 Kroyer being much superior to Bassett-Smith's substitute. 



GENERIC DIAGNOSIS. 



General form similar to that of Lepeophthelrus. Carapace elliptical, 

 much longer than the genital segment. Frontal plates well defined 

 and without lunules. Fourth thoracic (free) segment with small but 

 well-defined dorsal plates in the female; these plates very rudimentary 

 or entirel}' lacking in the male. Abdomen biarticulate. Anal laminae 

 relatively verv large and armed with long seta?. First three pairs of 

 thoracic legs two-branched, the exopods armed with stout, strongly 

 curved, corneous claws, much larger than those in other genera. Each 

 branch of the first pair biarticulate; of the other two pairs, triarticu- 

 late. Fourth legs rudimentary and invisible from the dorsal surface. 

 Furca lacking, but in its place appear two corrugated chitin ridges 

 arranged like the sides of a V, the apex pointing backward (fig. 18, 

 p. 696). Genital segment enlarged as in the Caliginte, without any 

 traces of fifth legs. Egg-cases and eggs as in Caligus^ usuallv quite 

 long. Development similar to that of the Caligina?, but in the chali- 

 mus stage the young are attached by means of their enlarged second 

 antennae, and there is no frontal filament. 



ANALYTICAL KEY TO SPECIES. 



1. Genital segment quadrangular, with rounded corners and without posterior pro- 

 cesses 2 



1. Genital segment spindle-shaped or lunate, with conical processes at the posterior 

 corners 4 



2. Males; genital segment less than one-third as wide as the carapace; abdomen 

 joints the same width 3 



2. Females; genital segment more than half the width of carapace; basal abdomen 

 joint nearly twice as wide as terminal glaber Wilson, 1905, p. 708 



3. Genital segment one-fourth longer than abdomen; the two joints of the latter the 

 same length difficilis van Beneden, 1892 



3. Genital segment one- fourth shorter than abdomen; terminal joint of latter nearly 

 twice as long as basal gracilis Wilson, 1905, p. 704 



4. Males; posterior processes of genital segment shorter than basal joint of abdo- 

 men; fifth legs showing at center of the lateral margins, 



glaber Wilson, 1905, p. 708 



4. Females; posterior processes of genital segment as long as, or longer than, the 

 entire abdomen; fifth legs not visible dorsally 5 



