350 



ALFRED GIBBS BOURNE. 



Oersted, and more recently mentioned by Czerniavsky, who 

 founded the genus Paranais for it and the above-mentioned 

 species. Czerniavsky found it in Abchasia. 



Professor Lankester received specimens of this worm from 

 the great mud-banks at Sheerness, at first through Mr. Bolton; 

 but we afterwards obtained it in quantity from Mr. W. H. 

 Shrubsole, who found it living in enormous numbers along 

 with Haplobranchus and Hemitubifex. It is one of the 

 few Oligochseta which are known to inhabit salt water. 



I am able to give only such notes of its structure as were 

 made at the time by Professor Lankester and myself. 



The prostomium is blunt and rounded. 



The setae present an arrangement the main features of which 

 are doubtless characteristic of the genus, and are given above 

 in the generic definition. 



Setse are absent, as is universally the case, from the peristo- 

 mial segment (segment i). 



In segments ii, iii, and iv, ventral seta bundles alone are 

 present, while in all other segments dorsal and ventral seta 

 bundles are present. The usual number of setse to the bundles 

 is as follows : 



Dorsal. Ventral. 



Segment i 



and 80 on. In the dorsal bundles there are occasionally two 

 setae only ; and in the budding region there are, as a rule, in 

 the early stages of the bud two setse only in each bundle, one 

 longer than the other. 



The ordinary setae vary but little in shape throughout the body. 



In no other genus of Naids have all the dorsal setae the 

 crotchet shape, as is here the case (PI. XXVII, fig. 6). 



In Ophidonais none of the dorsal setae are capillary, but are 

 spear-shaped setae, and unlike the ventral setae of that genus. 



In P. littoralis the setae of the cephalized segments are 



