DESCRIPTIONS OF GENERA AND SPECIES 259 



' incerfcae sedis.' I regard this genus and species as- distinct from Spirosperma ferox 

 (with which, on account of the integumental tubercles, it might be confounded), 

 for the reason that there are no setae but eapilliform setae in the dorsal bundles. 

 This peculiarity has been stated to occur by Geube in his species ' Saenuris vdutina,' 

 to which attention has been duly called by Vejdovsky, who considers further evidence 

 desirable before the absence of uncinate setae from the dorsal bundles can be regarded 

 as fully proved. It seems improbable that hoth Gbube and Leidt would have fallen 

 into error about a point of this kind, and, furthermore, it seems probable that 

 S. velutina is identical with EmbolocepJialus velutina (see below). Embolocephalus, 

 however, has only two setae on each bundle ; this worm can also retract the pro- 

 stomium and first segment, so that the body appears to commence with the first 

 setigerous segment. It inhabits the depths of the Lakes of Geneva and Zurich. 

 P. variegatus was found by Leidy in springs, the water of which was impregnated 

 with iron, in the neighbourhood of Philadelphia ; there is no mention of any power 

 of retracting the end of the body. I am disposed, therefore, to consider that the 

 genus Peloscolex is a valid genus, distinguishable from nearly all other Tubificidae by 

 the presence of eapilliform setae only in the dorsal fasciculus. 



It may be that ]}fais papillosa should be transferred from Spirosperma to the 

 present genus. 



Genus Psammoryctes, Vejdovsky. 



Syn. Saenuris, Kessler (in part.). 

 Tubifex, Lankestee (in part.). 

 Archaeoryetes, Czeeniavsky. 



Depinitiom". Setae eapilliform, uncinate, palmate, and pectinate. Spermiducal 

 glands, with a vesicula seminalis; prostate as in Tubifex; spermatheeae opening 

 in common with a muscular sac containing a single long seta ; appended to 

 this sac are two or four glands. 



The genus Psammoryctes has been investigated by Lankestee (2), Vejdovsky 

 (13, 24), Peeeiee (7), and, more recently, by Stolc (3); Vejdovsky established 

 its distinctness from Tuhifex, with which it had been confounded by Lankestee 

 and Peeeiee ; the differences which this genus shows from Tuhifex were still 

 further accentuated by Stolc, who described and figured the remarkable apparatus 

 in connexion with the apertures of the spermatheeae. These have been already 

 described (see p. 132). I quite agree with Vaillant in relegating Czeeniavsky's 

 Archaeo7'yctes to this genus. The only difference alleged by Czeeniavsky is that 



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