no. 2071. NEW GENUS OF DISCODRILID WORMS— HALL. 189 



male sexual products being liberated in the body cavity in these 

 segments. There are 2 or 4 spermaducts, according to the number 

 of testes, located in the dissepiments between segments 5 and 6 in 

 the first case and also in that between 6 and 7 in the second case. 

 The spermaducts open into a single atrium after each pair has united 

 to form a deferent vessel. The atrium always consists of an enlarged 

 distal portion and a narrower portion which forms a short bursa. 

 Within the bursa is the penis, usually eversible, though Cambarincola 

 macrodonta is listed as not having an eversible penis. The two 

 ovaries are paired on the dissepiments between trunk segments 6 

 and 7, and project into segment 7. Frequently 2 or 3 large eggs in 

 an advanced stage of maturation may be found in this segment. 

 The organ for the emission of these eggs consists of 2 funnel-like 

 ciliated pores in the latero-ventral wall near the posterior limit of 

 the seventh trunk segment. 



As a complement of the genital system, there is always in the fifth 

 trunk segment an unpaired spermatheca, opening in the middle of 

 the segment in the mid-ventral line. This is of variable form, 

 globular, flask-shaped, cylindrical, or more or less elongate-bifid, 

 extending into the following segment. The blind end is usually free, 

 but may be contracted against the dorsal wall by means of a peri- 

 toneal investment. Odier (1823) described the copulation of two 

 individuals. 



The discodrilids live on crayfish. They are not parasitic when 

 young, a study of the intestinal tract at this period showing vege- 

 table detritus and small animals. In the adult stage the teeth are 

 used to break the skin of the host animal in order to suck the blood. 

 I have found several pieces of striated, voluntary muscle fiber in the 

 intestine of the adult discodrilid described in this paper. 



According to Pierantoni (1912) discodrilids are recorded from 

 Europe, North America, oriental Asia, and Japan. Moquin-Tandon 

 (1846) lists 2 species, Branchiobdella cMlensis and Br. auriculae, from 

 Santiago de Chile, South America, designating them as not well- 

 known species. 



The features of systematic importance are the external form, 

 preoral lobe, structure of the dental plates and of the genitalia. 



According to Prof. J. Percy Moore (in correspondence) the name 

 Discodrilidae dates from Vejdovsky (1884) which is not available to me. 

 While this name has the family termination, it is merely a group name, 

 as there is no genus from which the name Diseodrilida? could be 

 derived. This name should be suppressed in favor of the f amily name 

 Branchiobdellidae. In the available literature I find Branchiobdel- 

 lidae first used by Ludwig (1886) , but it probably antedates that. As 

 these annelids make up a very distinct group, quite unlike other 

 annelids, I have proposed here the following classification. 



