INVERTEBRATE FAUNA OF LAKE SUPERIOR. G95 



ISOPODA. 



AsELLOPSis TEN AX Harger, (p. G59.) 



b:s^tomosteaca. 



CLADOCEEA. 



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



Om en i Sommeren 1862, foretagen zoologisk Reise i Christi.iuias og Troiulh jiMiis 

 Stiftor, p. 21, 18f)3, (teste Miiller ;) E. P. MiiUer, Deumarks Cladocera, Naturbia- 

 torisk Ticlsskiift, III, vol. v, p. 117, pi. 1, lig. 6, 1868. 



A species of Daphnia, which I camiot discover to diifer io the least 

 from Milller's description and beaiitifal fij^nres abova referred to, was 

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

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

 from 72 fathoms at the same localit3^ 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 in 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 preciselj^ 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 



DAtHNiA PELLUCIDA Miiller. 

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



The remarks in 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, anil in having 

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

 spines and the rest of the way with very slender sette, while in Z). galeata 

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

 their whole length. The front of the head is also more evenly rounded 

 and less crested than it erer is in Z>. 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 storaaclis fi^om Outer 

 Island. 



