AQUATIC EARTHWORMS 643 



41 (40) Spermathecae without diverticula, paired or two unpaired ones 



opening separately; long, highly muscular, ejaculatory 

 chamber forms part of each otherwise highly differentiated 

 sperm-duct Eelipidrilus Eisen 1881. 



A genus of peculiar North American Lumbriculidae which includes E. frigidus Eisen 

 from California, with paired $ pores on X; E. asymmetricus (Frank Smith) from Illinois, 

 with single median $ pore on X; and E. palustris (Frank Smith) from Florida, with paired $ 

 pores on IX (Smith, igooa). 



42 (36, 37) Earthworms, essentially aquatic in habit. Setae simple-pointed 



and paired in each of four bundles per somite; $ pores ex- 

 ceptionally on XII or XIII, commonly further posterior; 

 spermaries in X and XI; ovaries in XIII 43 



43 (44) Clitellum beginning on XIV to XVI and extending over 10-12 



somites; $ pores on XVIII/XIX or on XIX, recognizable 

 only in sections; few or no dorsal pores; without well- 

 developed gizzard Sparganophilus Benham 1892. 



Several North American species, of which S. eiseni Frank Smith is found in the Mississippi 

 Valley, Great Lakes region, and Florida; S. smithi Eisen and subspecies occur in California; 

 S. benhami Eisen and subspecies in Mexicoand Central America (Eisen, 1896). 



44 (43) Clitellum beginning on XVIII-XXIII and extending over 4-6 



somites; $ pores on XII, XIII, or XV, conspicuous; gizzard 

 limited to XVII; first dorsal pores on IV/V. 



Helodrilus Subgenus Eiseniella Michaelsen 1900. 



The highly variable species, H. (E.) tetraedrus (Savigny), is represented in North America 

 by several of the subspecies indicated in the diagram from Michaelsen (Fig. 993). 



12 13 14 15 l6 17 l8 19 20 21 22 23 24 25 26 27 28 



% ^^ *^ * form tyfita 



^-0 ' form hercynia 



form rteapolitana* 

 form Ninnii 

 form tetragonura 

 form pupa 



r-"e-~ 



FIG. 993. Different forms of Helodrilus (Eiseniella) tetraedrus (Savigny). The diagram shows 

 the positions for the spermiducal pores and the tubercula pubertatis. (After Michaelsen.) 



A specimen which is presumably the type of Helodrilus tetraedrus forma pupa (Eisen) 

 was deposited in the United States National Museum and has been studied by the writer. 

 It is almost certainly a regenerated individual and is highly abnormal and hence the form 

 presumably has no systematic status except in synonomy. References in paragraphs 42 and 

 44 of the above key and in Fig. 993, to spermiducal pores on XII, have therefore lost their 

 significance. 



Beside these essentially aquatic forms, several species of Diplocardia and Helodrilus live 

 in bottomlands and low-lying banks of streams which are subject to overflow for prolonged 

 intervals 



