22 BRISTOL. [Vol. XV. 



" When a larger series of living specimens from various locali- 

 ties can be studied, the three preceding forms {N. lateralis, 

 N. qjtadristi'iata, N. marmorata), admitted here as distinct, may 

 prove to be mere varieties of one species, no less variable than 

 N. vulgaris of Europe." The fourth species, N. fervida, is 

 described from specimens taken from Lake Superior and has 

 eight ocelli. I have not collected a Nephelis answering to this 

 description. 



The genus is widely distributed in the United States. My 

 own collections have been made in Massachusetts, Connecticut, 

 Illinois, New York, and South Dakota. I have received speci- 

 mens from Mr. A. J. Hunter, of Toronto, collected near To- 

 ronto, Can., and Professor Forbes, of the University of Illinois, 

 kindly loaned me for examination the specimens of Nephelis 

 collected by him in the Yellowstone region in 1890. Verrill 

 records collections from Maine, Massachusetts, Connecticut, 

 New Jersey, Wisconsin, Nebraska, Colorado (at an elevation 

 of 9000 feet on Longs Peak), and from the waters of Lakes 

 Superior and Huron. The area included covers about 35 

 degrees of longitude and 10 degrees of latitude; it embraces 

 the Atlantic slope, the Great Lake Region, the Missouri Valley, 

 and the Rocky Mountains. 



Investigations on my own collections lead me to agree with 

 Savigny, Moquin-Tandon, and Verrill that it is difficult to dis- 

 tinguish species by the criteria used by them, color and color 

 markings, and to disagree with the methods and results, pub- 

 lished by Lindenfeld and Pietruszynski (6), who rely on these 

 features exclusively. My first attempts to classify the specimens 

 which I collected were naturally based on the descriptions given 

 by previous investigators, but it proved so difficult a task to 

 determine what value to place on the various statements of color, 

 and so many of my specimens could with equal propriety be 

 placed in either of two or three categories, that it became 

 evident that some different method of diagnosis would be 

 necessary. The necessity of going beyond color markings was 

 plainly shown by the following experiments. 



* Von Lindenfeld und Pietruszynski: " Beitriige zur Hirudineen fauna Polens." 

 Reviewed by Nusbaum. Biol. Centralblatt, Bd. xii. p. 55, 1892. 



