HIRUDINEA 317 



Leeches are mostly aquatic animals which live in fresh water in all 

 parts of the world ; a few live in the sea and a few in moist earth. They 

 are predacious animals, feeding on oligochaets, snails, and other small 

 animals and are also at times external parasites, sucking the blood of 

 aquatic vertebrates. The class contains two orders and about 150 

 species. 



Key to the orders of Hirudinea: 



a x Proboscis present and no jaws ; blood colorless ; somites rarely consisting 



of 5 rings each 1. RHYNCHOBDELLIDA 



a a No proboscis but usually 3 jaws present ; blood red ; somites usually 



consisting of 5 rings each 2. GNATHOBDELLIDA 



ORDER 1. RHYNCHOBDELLIDA.* 



Leeches with a proboscis which can be thrust out of the mouth, and 

 no jaws, and with colorless blood; segments consisting of 3 or more but 

 rarely of 5 rings each : 2 families. 



Key to the families of Rhynchobdellida: 



d! Both suckers distinct from body 1. ICHTHYOBDELLIDAE 



c, Hinder sucker distinct, forward sucker more or less fused with body. 



2. GLOSSIPHONIIDAE 



FAMILY 1. ICHTHYOBDELLIDAE. 



Leeches parasitic on fishes, tortoises, and some other animals; both 

 suckers pedunculate; body elongate, narrow anteriorly, and broad pos- 

 teriorly; body segments containing more than 3 rings each: 7 genera. 



Key to the genera of Ichthyobdellidae here described: 



a x No gills present 1. PiSdCOLA 



a 2 Gills present. 



61 Paired papilliform vesicles act as gills 2. CYSTOBBANCHUS 



6, Paired arborescent gills present 3. BBANCHELLION 



1. PISCICOLA Blainville. Body cylindrical, distinctly 

 annulated with many (usually 14) rings to a somite; eyes 

 distinct: many species. 



P. rapax (Verrill) (Fig. 498). Body long and slender, 

 dark olive in color with a row of rectangular white spots 

 along each side; length 40 mm.; width 2 mm.: on the 

 summer flounder. 



P. funduli (Verr.). Body smooth, distinctly annu- 

 lated, light green in color with fine dots of brown and 

 green; length 18 mm.; 2 large and 2 small eyes: on Fundulus 

 pisculentus. 



* See "Some North American Freshwater Rhynchobdellida and The.ir Parasites," 

 by W. E. Castle, Bull. Mus. Comp. Zool., Vol. 36, p. 17, 1900. 



