HEKATEEOBRANOHUS SHRUBSOLII. 197 



Cephalic tentacles not grooved, but ciliated all over. 



Prostomium well developed, bearing four eyes. 



1st segment prolonged forwards on the ventral surface to 

 form a collar. 



Pharynx evertible and richly ciliated. 



A single pair of thoracic nephridia, opening to the exterior 

 in the 2nd segment, reaching back into the 6th segment, and 

 thence bending forwards again. 



Giant-fibres minute, one in each nerve-cord near the upper 

 and inner surface. 



Dorsal " cirri " forming a sort of collar in the 2nd segment. 



H. Shrubsolii, sp. n. 



The following characters are probably of specific value. 



Ventral crotchet chsetse begin in 8th segment, accompanied 

 by a few capillary chcetse. 



Shape of chtetse (fig. 4). 



Sinus round intestine posteriorly. . 



Intra-vascular ridge in dorsal vessel. 



Thoracic nephridia green. 



Habitat. — The mouth of the Thames.^ 



Postscript. 



Whilst the foregoing paper was in the press I succeeded 

 in obtaining Webster's original description of the genus S tre- 

 ble spio, which is in the 39th Annual Report of the Trustees 

 of the New York State Museum of Natural History. Had I 

 seen the full description of this genus earlier, I should have 

 been loth to make a new genus for a form which may well be 

 included in Webster's genus. But having seen a figure of the 

 head of Streblospio, and this not even suggesting to me 

 the identity of the genus I was studying with the one figured, 

 I contented myself with merely mentioning (p. 190) what 

 appeared to be one point of resemblance between the two 



^ Mr. Shrubsole informs me that he has found both this form and Haplo- 

 branchus as far up as Graveseud on the south side of the river. 



