886 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [8] 



tapering-. The tenth segment is thicker than any other two segments, 

 and forms a well deflned-cinguliim in adult specimens. 



Habitat. — Europe, Sweden : Motala River, in shallow water, togethe: 

 with Hemitubifex and Lumbriculus. Professor W. Lilljeborg has als« 

 kindly communicated specimens taken in Ifo Lake, in Scania; here, how 

 ever, found at a depth of 25 fathoms. 



The specimens from both places were pretty much alike, except U 

 regard to the helix like swelling of the atrium, which was absent in thi 

 specimens from Ifo. 



It may be possible that a worm described by Kessler,* under the 

 name of Wais papillosa, is identical with our present species. Th( 

 length of the body and the ^^papillce^^ are similar in both species. Kegs 

 ler's description is, however, so insufficient that nothing can be decidec 

 with any degree of certainty, except by autopsy. External character 

 istics are in no way sufficient to distinguish one species from the other 

 and have only a relative value as a help in classifying and arranging 

 the specimens in a collection, when it oftentimes is of the highest im 

 portance that said work cap be done quickly and without destruction 

 or mutilation of the specimens. 



Gen. ILYODEILUS nov. gen. 



The cephalic ganglion emarginated both in front and behind. 



The efferent duct is, compared with the same duct in other genera o 

 the family, short and broad. Its length does never exceed the lengtl 

 of the atrium and penis together. The whole of the atrium is glandu 

 lar and its lower end is comparatively broad and short. Ko vesicuh 

 seminalis. No glands at the base of the receptacle. No spermato 

 phores. The oviduct is funnel-shaped, the upper end being the widest 

 The spines are of three kinds, viz, hair-spines, comb or fan-like spines 

 and forked spines. The gap between the prongs of the fan-like spinej 

 is comparatively narrow, and the striated membrane between the prong! 

 not always present. In other respects this genus resembles Ttibifet 

 and Psammoryctes. The form of the efferent duct is the most promi 

 nent characteristic of the genus. 



Only three species are as yet found, and whicb may easily be classifiec 

 as follows : 



1. True comb-like spines present. The recejjtacleisbent; oviduct is double; cephali 



gauglion about as broad as long. 



II. Perrierii 



2. Pseudo comb-like spines. The receptacle is bent; oviduct is single; cephalic gar 



glion is broader than long. 



II. S0DALI8 



3. Pseudo comb-like spines. The receptacle is not bent, but globular and inflated 



cephalic ganglion about as broad as long; oviduct is single. 



II. FRAGILI8 



* Beitriige zu der Abhandl. der Petersburger Nat.-forsh. Versaml. 1868, pp. 103 to 

 108. Leuckarts Bericht, 1871, 



