[7] LAKE SUPERIOR ENTOMOSTRACA. 707 



from the European, so far as I have seen, in a few slight particulars— 

 especially interesting because of their minute and trivial character ; but 

 in every detail of any importance the New and Old World individuals 

 are alike, so far as I can judge from the original description of Sars* 

 and from the amply illustrated paper of Xordqvist. t 



The minute terminal segment of the antennae, the twenty-fifth of the 

 European form, is in our examples consolidated with the preceding, so 

 tha*t there are but twenty-four segments, and numbers 8 and 12 are 

 without the hook-like spines mentioned by Nordqvist. The armature of 

 the mandible is somewhat reduced, consisting in the American form 

 of seven short teeth, the two lower acute and widely separated, and the 

 five remaining blunt and emarginate at tip. At the upper end of this 

 series is a slender, acute tooth, and a small simple hair. There is uorow 

 of accessory spines on the mandible, as figured by Nordqvist. 



The slight differences noted are in the direction of a higher special- 

 ization, and suggest, as do those of the Diaptomi, that our American 

 variety has had a more rapid course of development than the European. 



In the Old World, Limnocalanus has been found only in the larger 

 lakes of Finland and Scandinavia, and in the gulfs of the Baltic (Fin- 

 land and Bothnia). It seems to have been distributed in company with 

 Diaptomus sicilis, and later than Epischura; and is probably now isolated 

 from its European brotherhood— a geographical variety on the way to 

 become a species. 



Family Harpactid^e. 

 Canthocamptus, sp. 



Only a few specimens of this genus of minute Copepoda have been 

 found in my Lake Superior collections, and in the one from Lake Michi- 

 gamrae— a number too small to permit a study of the species. 



Family OyclopiDvE. 



Cyclops thomasi Forbes. (PI. n, fig. 8.) 



Cyclops thomasi Forbes, Amer. Nat. xvi (1882), p. 649 ; Cragin, Trans. Kan. Acad 

 Sci., viii (1882-'83), pp. 68-70.) 



This well-marked species — the commonest of Lake Superior, where 

 it is the usual companion of the Great Lake Diaptomi— was taken in 

 nearly every haul, often in countless numbers. It is a species of clear 

 water and the open lake, and was far less frequent at L'Anse Bay than 

 at Marquette and White Fish Point. In Lake Michigamme it was not 

 seen. 



Cyclops gyrinus, n. sp. (PJ. n, fig. 9; PI. in, fig. 14). 



A stout, heavy species, with long first segment, strongly arched 



*Oversigt af de indenlandsko Ferskvandscopepoder. Forband. i Vidensk.-Selsk. 

 i Christiania, p. 226. 

 t Die Calaniden Finlands, p. 31, 



