280 A MON^OGRAPH OF THE AUSTRALIAN APHRODITEA, 



The ventral setse in this species (figs. 5 and 6) are 25-30 in 

 number, stout, and of a form very common among the members 

 of this genus ; the terminal portion of the seta, namely, is bent 

 back on the rest at a very obtuse angle, and is armed from the bend 

 to near the apex with two rows of slender spines, about a dozen 

 in number in each row, the last being larger than the rest. The 

 dorsal setse are much more numerous than the ventrals, are 

 about ^rd of the thickness of the latter, nearly straight, with an 

 acute apex, and some smooth, while others are ornamented with 

 numerous transverse rows of exceedingly minute spinules. The 

 elytra are dotted here and there on their upper surface with 

 larger and smaller hollow ciliated processes (fig. 8). The 

 preestomial tentacles are nearly always subequal, but vary some- 

 what in this respect ; they and the peristomial tentacles and cirri 

 are ornamented with brown bands. 



This is the commonest species of the order in Port Jackson. 

 It is found among beds of mussels both between tide marks and, 

 more rarely, in deeper water. It is of very sluggish habits, and 

 is incapable of voluntarily parting with its elytra, which, when at 

 rest, it habitually holds in an oblique position well off the dorsal 

 surface. 



I was at first disposed to identify the species which I here 

 refer to T. argus, with Lepidonotus oculatus of Baird, but the 

 latter is placed by Baird in the genus Lepidonotus, and a distinct 

 genus created for those species which differ, like the above, from 

 the typical species of Lepidonotus in having the elytra small and 

 not overlapping across the middle of the back ; in other points 

 L. oculatus and T. argus seem nearly related. 



A specimen of what seems to be a variety of this species (figs. 

 9 — 11) was dredged by me at Griffiths' Point, Western Port. It 

 differs slightly from the Port Jackson form in the shape of the 

 ventral setae and other minor points. 



