AET. 4 ; SENECELLA CALANOIDES JUDAY 5 



somewhat coalesced. Likewise the mandible, the maxilla, and the 

 first maxilliped are like those of the female. 



The absence of the fifth pair of swimming legs in the female, 

 the reduction of three oral appendages in the adult male, and the 

 fact that the right member of the first pair of antennae is like the 

 left in the adult male serve to distinguish Senecella calanoides from . 

 the other fresh-water Calanoida that are known at the present time. 

 These characters give it a much closer relationship to some of the 

 marine calanoids than to the other fresh-water members of this 

 group. 



Distribution. — Senecella calanoides was obtained from the lower 

 water of Seneca Lake and of Cayuga Lake, N. Y., in September, 

 1908, in August. 1910, and in July, 1918, and from Owasco Lake 

 in August, 1910. Through the kindness of N. K. Bigelow of the 

 Eoy'al Ontario Museum of Zoology and of Dr. W. A. Clemens of the 

 University of Toronto, plankton material containing Senecella has 

 been obtained from two Canadian lakes, namely, Lake Timagami 

 and Lake Nipigon. 



In a person'al communication dated May 8, 1924, Dr. C. Dwight 

 Marsh states that he collected immature specimens of an unknown 

 copepod in Pine Lake, Michigan, in 1894, and in Lake Superior 

 near Duluth, Minn., in 1898, and he now finds that these juvenile 

 specimens are identical with those of Senecella calanoides from Sen- 

 eca Lake. 



In a recent note - attention was called to the fact that Senecella 

 was not associated with Lhnnocnlanus in the New York lakes, but 

 the material from Lake Nipigon contains both forms, the latter being 

 much more abundant than the former. In the New York lakes Sen- 

 ecella was not present in the upper 15 meters of water in the sum- 

 mer, but in Lake Nipigon it has been taken where the water was 

 less than 2 meters deep. 



EXPLANATION OF PLATES 

 Plate 1 



Fig. 1. Dorsal view of female, X 28. 



2. Side view of female, X 28. 



3. First antenna of female, X 43. 



4. Second antenna of female, X 75. 



5. Mandible of female, X 114. 



6. Maxilla of female, X 114. 



« Science (new ser.), vol. 58, 1923, p. 205. 



