CYCLOPID^E AND CALANID^E OF MICHIGAN LAKES. 11 



E. lacustris was a common species in the collections from Lake St. Clair,. 

 Lake Michigan, and many of the smaller lakes. 



Genus LIMNOCAL.ANUS Sars. 



LlMNOCALANUS MACRURUS SarS. 

 Plate IV, figs. 1 and 2, Plate V, fige. 1-5. 



1863. L. macrurus Sars., pp. 228-229. 



1882. " " Forbes, p. 648. 



1886. Ceritropages Grimaldi DeGuerne, pp. 1-10. 



1888. L. macrurus Nordqvist, pp. 31-37, pi. I, figs. 9-11; pi. II, figs. 



1-5; pi. Ill, figs. 1-4. 



1889. L. macrurus DeGuerne and Richard, p. 77, pi. IV, figs. 5. 11, 



and 12. 

 1891. L. macrurus var. auctus Forbes, p. 706. 

 1893. " " Marsh, p. 201, pi. IV, fig. 7. 



For the description of L. macrurus we must depend largely upon the 

 elaborate description and figures of Nordqvist. 



Forbes ('91, p. 706) thinks that our form is sufficiently different from 

 the European to rank as a distinct variety. When preparing my former 

 paper ('93) it did not seem to me that there was good reason for establish- 

 ing a new variety. Recently I have made a more careful examination of 

 the details of its structure, using material from Detroit River, Lake Mich- 

 igan, and Green Lake. So far as the specimens I have examined are con- 

 cerned, the points of difference mentioned by Forbes ('91, p. 707) do not 

 exist. It seems to me that the twenty-fifth antennal segment is clearly 

 separated from the twenty-fourth, and not consolidated as stated by him. 

 In all my specimens I find the hook like spines on the eighth and twelfth 

 segments. 



Nordqvist and Forbes are in agreement in regard to the terminal teeth, 

 of the mandible, but Forbes finds one seta instead of the two figured by 

 Nordqvist; in this respect my observations confirm those of Forbes. The 

 accessory spines have been evident in my preparations. It would seem 

 then, that unless L. macrurus is susceptible of local variations — a highly 

 improbable supposition — that Forbes's variety can not stand, for the only 

 point of difference on which it rests is the existence of one seta on the 

 mandible instead of two. 



The second joint of the second maxillipede differs slightly from Nord- 

 qvist's figure, and I have accordingly figured it. (PL V, fig. 5.) The 

 difference appears to me, however, unimportant. 



It is impossible to tell whether our species may not differ from the 

 European in the armature of the antenna, as that was not worked out in 

 detail by Nordqvist. In regard to the sensory setae, he simply states that 

 they are present on some of the segments, but does not state their number. 



In the female, clavate sensory setae are present on all joints except the 

 4th, 20th, 21st, 22d, and 24th. The setae are distributed as follows: the 

 first joint has three; there are two on the 2d, 3d, 5th, 7th, 9th, 10th, 11th 

 13th to 19th inclusive, and 22d to 24th inclusive; the 4th, 8th, 12th 20th,. 



