INVERTEBRATE FAUNA OF LAKE SUPERIOR. 695 



ISOrODA. 



ASELLOPSis TENAX Harger, (p. 659.) 



EXTOMOSTEACA. 



CLADOCERA. 



Daphnia galeata G. O. Sars. (Plate II, fig. 11.) 



Om en i Sommerea 1862, foretagea zoologisk Reise i Christiauias og Trondhjems 

 Stiftor, p. 21, 1863, (fesfe Miillei- ;) E. P. Miiller, Denmarks Cladocera, Xaturhis- 

 toiisk Tidsskrift, III, vol. v, p. 117, pi. 1, fig. 6, 1868. 



A species of Daplmia^ whicli I caunot discover to differ iu tlie least 

 from Miiller's descriptioa aud beautiful figures above referred to, was 

 taken quite abundantly near the surface of the water a few miles south 

 of Saint Iguace Island August 29, 1871, and was found in the dredge 

 from 72 fathoms at the same locality. It was also found in the deeper 

 dredgings in many parts of the lake, but was very likely taken each 

 time near the surface in the dredge on its way up. A few specimens 

 occurred iu the stomachs of the white-fish taken at Outer Island and at 

 Sault Sainte Marie. 



This and the next species are transparent, and seem to be free-swim- 

 ming animals, inhabiting the waters of the lakes away from the weedy 

 shores or bottom, where most of the other species of the genus are 

 found. In Europe, this species is found in the lakes of Scandinavia and 

 Denmark, where it appears to have precisely the same habits as in Lake 

 Superior. 



It is possible that a minute comparison, of specimens from Europe and 

 America may reveal some differences similar to those which I have 

 noticed in the species of Pontoporeia from the two countries, but with 

 the figures and description referred to I can find absolutely no differ- 

 ences. The American specimens exhibit the same varieties of form in 

 the head and teste as are described by Miiller in European specimens 



Daphnia pellucida Miiller. 



Op. cit., p. 116, pi. 1, fig. 5. 



The remarks iu regard to the identity of the last species apply equally 

 to this. This species differs from the last in having the rostrum some- 

 what acute and curved backward instead of truncate, and in having 

 the caudal stylets armed near the base with a series of slender teeth or 

 spines aud the rest of the way with very slender sette, while iu Z). galeata 

 they are without teeth or spines, and are furnished with setie through 

 their whole length. The front of the head is also more ev^enly rounded 

 and less crested than it ever is in I), galeata, although that species 

 varies much in this respect. 



This species was taken at the same times and places as the last, and 

 was also found among the contents of white-fish stomachs from Outer 

 Island. 



