1 8 BRISTOL. [Vol. XV. 



for aid and advice, and to Prof. S. A. Forbes, of the Uni- 

 versity of Illinois, for the privilege of examining the specimens 

 of Nephelis collected by him under the auspices of the U. S. 

 Fish Commission in the Yellowstone region in Wyoming. 



Historical. 



In 1 767 Linne enumerated nine species of leeches in one genus, 

 Hirudo. This classification was followed by most later authors, 

 for example, Cuvier, Blumenbach, Carena, and Dumeril, until 

 about 18 1 7, when Savigny, in his Systcnic dcs Annclides, 

 announced the separation of Linne's genus into seven genera. 

 The name Nephelis appears in this work for the first time, 

 although Oken set this leech apart from Hirudo in 1815 under 

 the name Helluo, which genus was to include all fresh-water 

 leeches not provided with jaws. In 18 18 Lamarck, at the 

 suggestion of Blainville, proposed the name Erpobdella, which 

 Blainville (1828) urged for acceptance because it contained the 

 descriptive part " bdella." In 1826 Moquin-Tandon adopted 

 Savigny's name Nephelis and continued it in the second edition 

 of his Monograpinc dcs Hirudin^cs (l). The name has since 

 become generally accepted, notwithstanding the fact that 

 Oken's Helluo holds priority and Lamarck's Erpobdella is 

 more descriptive. 



The first description of Nephelis in America was made by 

 Thomas Say (2) in 1824 under the name of Hirudo lateralis. 

 In 1872 Verrill (3) changed this to Nephelis lateralis, which, for 

 reasons given in another part of this paper, I have given to the 

 leech I have studied. 



Methods. 



The leeches are easily kept in aquaria, for which I used the 

 low glass dishes known as crystallizing dishes, or white earthen- 



1 A. Moquin-Tandon : Monographie de la famille des hirudinees. Paris. 1846. 



'^ T. Say : Major Long's Second Expedition to the Source of St. Peter's River, 

 vol. ii, Appendix to the Natural History. 1824. (Republished in Diesing's 

 Systhne Hehnhtthologique., vol. i.) 



' A. E. Verrill : " Synopsis of the North American Fresh-water Leeches." U. S. 

 Fish Commissioner's Report for 1872-74. (Refers to the American Journal of 

 Science, vol. iii, 1872.) 



