North American Centropagidce. 243 



Limnocalan us, L. grimaldii de Guerne. Except for a difference 

 in size and in the proportions of the segments of the fifth legs 

 of both sexes, which segments are somewhat less robust in 

 the fresh-water form than in the one from the Caspian Sea, 

 and but for a slight though noticeable difference in the lateral 

 aspect of the head, the two forms exactly correspond. It 

 does not seem to me that such slight differences warrant the 

 establishment of a new variety, much less of a new species. 

 With the exceptions just noted, the details of structure men- 

 tioned in the foregoing description are equally prominent in 

 both forms, as are those noted in the following discussion of 

 the published figures of the species. 



The best illustrations of L. mqcrurus are given in "Die 

 Calaniden Finlands " (Nordqvist, '88) and in the "Revision 

 des Calanides d'eau douce" (de Guerne et Richard, '89b), 

 although in neither publication are they strictly correct. 1 )e 

 Guerne and Richard's figures of the fifth pair of legs of the 

 female do not show the projection of the second basal seg- 

 ment over the first segment of the outer ramus, nor the hairs 

 on the inner margin of the second segment of this ramus and 

 on the third segment of the inner ramus, nor the serrations on 

 the spine at the outer apical angle of the last segment of the 

 outer ramus. Nordqvist says that the outer ramus has three 

 segments but figures it with two. The inner ramus he repre- 

 sents as smooth on the outer margin of all its segments, and 

 gives the ordinary form to the outer of the two setae on the 

 apex of the last segment of the outer ramus, while de Guerne 

 and Richard picture it with a hyaline lamina on both margins 

 and a few fine spinules on the inner margin. Neither is cor- 

 rect with regard to this seta, since it is plumose on the inner 

 margin and has a hyaline lamina on the outer one. 



Both de Guerne and Richard's and Nordqvist's figures of 

 the fifth pair of legs of the male fail to show the hairs on the 

 inner margins of the inner rami, the hyaline processes on the 

 outer margin of the second basal segment of the left leg and 

 on the first segment of the right outer ramus, and the serra- 

 tions on the hook of the last segment of the left outer ramus. 

 Further, Nordqvist fails to figure the hyaline process on the 



