294 OLIGOCHAETA 



segment. Ventral setae of segments II and III about one-third longer than setae of 

 other segments. Five or six setae in the anterior bundles, seven or eight in the others. 

 Twelve to fifteen setae in three anterior dorsal bundles, all very long. Hob. — Europe. 



This species has been chiefly studied by Vejdovsky (24, PL ii, figs- S-xa). 



(a) Ripistes maeroehaeta (Bourne). 

 Pterostylarides maeroehaeta, BoxJENB, Q. J. M. S., vol. xxxii, p. 349. 

 Definition. Prostomium mmch longer than peristomial segment. Ventral setae bundles of 

 segments II and III consist of two or three setae, those of other segments of two to five 

 setae. Three anterior dorsal seta bundles contain each two to five very long setae, the rest 

 being shorter than the other dorsal setae. Hob. — -Vlngland. 

 This species was described, with an illustration, by Bourne, in 1891. The descrip- 

 tion is limited to the external characters which alone are . indicated in the figure. 

 A note appended to the description of the species by ' E. R. L.' states that ' the long 

 setae are frequently found thrown forward so as to partly encase and protect the head 

 when the worm forms for itself a temporary tube. They are also used to strike the 

 water in swimming.' 



Genus Unoinais, Levinsen. 



8yn. Paranais, Czerniavsky. 

 Nais, AuCT. 



Clitellio, Vaillant (in part.). 

 Ophidonais, Vejdovsky (in part.). * 



Enehytraeus, Minor (in pai-t.). 

 Defiktitioit. Setae entirely uncinate ; dorsal setae commence in segment V. On 

 segment V of sexually mature individuals genital setae replace the ordinary 

 ventral setae. Glandular ventricle present. ISa nephridia (?). Testes (one 

 pair) in VIII and IX. Ovaries in X. Spermathecae in V. Eyes absent. 



The only well-known species of this genus is TJ. littoralis ; under this heading the 

 synonymy of the species and genus will be discussed. 



The above generic definition is entirely compiled from Bourne's (5) notes upon 

 U. littoralis, which establish its generic rank. Bourne figures a budding worm and 

 also the reproductive organs and setae of the sexually-mature worm. The most 

 remarkable external characters of the genus are the existence of uncinate setae only, 

 in both dorsal and ventral setae, and the absence of the dorsal setae from all segments 



