142 TWELFTH ANNUAL REPORT. 



dum colore albido, iuterdam vero facia transversa lata coloris fusci saturati in medio 

 cephalothorace ornatum. Longit. femiute parum supra 1 mm." 



The two forms following are suflBcieiitly distinct fro n the above 

 and form a closer link with the marine Calanidfe. It is doubtful if 

 any absolute line of demarkation exists between these varieties, 

 although they are here distinguished. 



Sp. 9. Diaptomus pallidns, Herrick. 

 ( Plate Q. Fig. 17.) 



Length 1.20 mm.; length of antennse 1.35 mm. Colorless. Head 

 separated by a suture into two parts; form very slender. Antennae 

 with elongated sette, which are very plumose. The right male an- 

 tenna has no hook. The inner rami of the fifth feet are one-jointed 

 in both sexes. Left foot of the fifth pair of the male of peculiar 

 form (see plate Q, fig. 17, for an extreme instance). Entire Missis- 

 sippi valley. 



var. sicilis, Forbes. 



(Plate Q. Fig. 18.) 



Like the above, but larger. Length 1.1:5 mm. Length of an- 

 tennas 1.5 mm. Inner ramus of male feet of fifth pair two-jointed, 

 those of the female one-jointed. The fori;n of feet varies a little 

 from the above. This species has been but once encountered in 

 Minnesota, the previous species occurring abundantly in our larger 

 lakes. 



D. kentuckyensis. Chambers, is referable to one of the above species, probably D. 

 longicornis. 



For a full account of synonymy see Rehberg, Beltrag z. Kenn.d.freile'b, Suesswasser 

 Copepoden, p. 552. 



VI. — Genus Lim:nocalanus, Sars. 



Cephalothorax 6-jointed, slender; abdomen in the female 3- 

 jointed, in the male 5-jointed. Antennae shorter than the body, 

 25-joiuted. Caudal stylets long. Feet of the four anterior pairs 

 with both rami 3-jointed; external ramus of the fifth foot in the 

 female 3-jointed, second joint produced into a spine ; inner rami 

 3-jointed in both sexes and like those of the previous pairs; external 

 rami 2-jointed in the male, the right and left dissimilar. 



