DESCRIPTIONS OF GENERA AND SPECIES 285 



This species is referred by recent systematists (VEJDOVSKY, BOURNE, and others) to 

 a distinct genus. I prefer to follow D'UDEKKM and LEVINSEN in regarding it as 

 congeneric with N. elinguis, &c. If any species of this genus is to be removed from 

 the others, it should be O.josinae. The only character upon which a generic definition 

 could be based is the long prostomium. Were we acquainted with a considerable 

 number of species showing this character, it might be advisable to give it generic 

 value. In the meantime, as there is only one species certainly known, it seems more 

 consistent to lay stress upon the similarity in the cephalization with other species. 



This Annelid is one of the best known. It has been studied by BONNET, TBEMBLEY, MULLER, 

 GRUITHUISEN, TAUBER (2, 3), VEJDOVSKY (24), and others. 



There is absolutely nothing in the very imperfect description given by LEIDY of his two species 

 'Stylaria paludosa,' and ' Styhtria fossularis' to enable one to understand on what grounds they are 

 separated from ' Stylaria lacustris.' 



The worm measures 10-15 mm. in length; the prostomium is long and slender- 

 its length is put down by MULLER as equal to ten segments of the body. The setae 

 of the dorsal bundles (two or three to each bundle) are long and capilliform ; the 

 ventral setae (four to six per bundle) are sigmoid and cleft at the extremity ; there 

 is sometimes a median swelling. BOURNE ' occasionally observed specimens in which 

 dorsal setae were present in the one or two most posteriorly placed of the usually 

 cephalized segments." 



The species is illustrated by BLAINVILLE (PL xxiv, fig. 3), CUVIEB (PL xxi, 

 figs. 2, 2 a), DALYELL (PI. xvii, figs. 6, 7), D'UDEKEM (4, PI. Hi, figs. 17-31), VEJDOVSKY 

 (24, PI. Hi, fig. 27, PL iv, figs. 1-24, 26-31). 



(4) Nais serpentina, 0. F. MULLER. 



N. serpentina, 0. F. MULLER, Verm, terrestr., vol. i, pt. ii, 1774, p. 20. 

 Ophidonais serpentina, GERVAIS, Bull. Ac. Roy. Belg. 1838, p. 19. 

 Serpentina quadristriata, OERSTED, Nat. Tidsskr. 1842, p. 134. 

 ? Ophidonais vermicularis, GERVAIS, Bull. Ac. Roy. Belg. 1838, p. 19. 

 Slavina serpentina, BousFiELD, J. Linn. Soc. 1886, p. 268. 



Definition. Dorsal setae short, straight, an/I bifurcate. Ventral setae of first four bundles 

 wit A a median thickening; on setae of posterior segments the swelling nearer the fixed 

 end. Three or four pigmented lands on segments II- V. Nad. Europe. 



This species, described by ROSEL and 0. F. MULLER (2) (by the latter under the 

 name of 'Die geschlangeltc Naide') in the last century, has been chiefly studied by 



