292 A MONOGRAPH OF THE AUSTRALIAN APHRODITEA, 



This species is somewhat nearly allied to the preceding, bat 

 the differences in the proportions of the tentacles and the numher 

 of the segments are constant. Both these species particularly 

 A. ascidiicola, are characterised by their very great activity 

 and the astonishing celerity of their movements, as well as the 

 readiness with which, when irritated, they part with their elytra, 

 Very numerous specimens of this species were found among the 

 colonies of an Ascidian obtained with the trawl at the mouth of 

 the Parramatta River. Allied to this species, though probably 

 distinct, is one which occurs under stones near high-water mark 

 in Port Jackson, and which is charactarised by the thickness and 

 density of its elytra. The head of this species {A. pachylepis) of 

 which I have only seen one specimen, unfortunately mislaid, is 

 represented in plate ix., fig. 17, and the minute structure of the 

 elytra in plate x., fig. 1. 



Genus Polynoe, Savigny. 



Polynoe asterolepis, sp. n. (PL X., figs. 3 — 7.) 



There are 49 setiferous segments in the only specimen of this 

 species which I have found, but several of the posterior segments 

 have been lost. The head is large : the mesial tentacle is more 

 than twice the length of the head, with a thick basal portion and 

 acuminate at the extremity ; the lateral preestomial tentacles are 

 shorter than the mesial, and of similar shape. The inner peri- 

 stomial tentacles are large and thick, extending beyond the 

 extremity of the mesial tentacle, and are subacute ; the outer 

 peristomial tentacles are smaller than the inner, and of a shape 

 similar to that of the preestomials. The parapodia are not 

 divided, the notopodium being represented only by an aciculum. 

 The ventral setae are of two kinds, viz. (1) slender, curved setae, 

 provided with two rows of serrations (spines) in their distal 

 portion, and (2) stouter setae with the form of those of Thormora 

 argus, but with a tooth near the apex. The scales, of which there 



