21. DioNcus BADius. Bodj half as broad as long, of a reddish-brown color, 

 above, with a flake-white dust internaixed. Anteriorly there are two colorless, 

 slightly prominent, circular knobs, which contain, scattered over the whole sur- 

 face, the very numerous and minute eyes. Below, the body is of a pale sepia 

 color, except the white digestive organs ; and the mouth is placed behind the 

 centre. Length, 1.5 inches; breadth, 0.75 inch. Found under stones in the 

 littoral zone. 



Hab. Australia, at Port Jackson. 



22. DiONCus OBLONGus. Oblong-oval, of a pale, transparent, brownish-grey 

 color above. Eye-clus'ers two, black, conspicuous, each surrounded by a ring 

 of white; the few large eye spots being crowded together at the summit only of 

 the oculiferous knobs. Length, 1 inch ; breadth, 0.35 inches. Found under 

 stones in the littoral zone. 



Hab. Australia, at Port Jackson. 



23. Thysanozoon Australe. Oval, rather broad, of a dark color, mottled 

 with blackish and brownish above; papillaj large, about sixty in number, nearly 

 equal in size on all parts of the body. Eyes numerous, in an oval white patch 

 between the bases of the tentacula, which is nearly divided in two by a wedge- 

 shaped clear space entering from behind. Length, 1 inch ; breadth, 0.6 inch. 

 Found on soft sponges in the circumlittoral zone. 



Hab. Australia, at Port Jackson. 



24. Valencinia annulata. Elongated, convex above : head broad, abruptly 

 truncated in front with a slight sinus at the middle, rounded at the sides and 

 narrowing gradually to the neck. Color purplish-brown, with a pale-yellowish 

 band across the head, and a narrow white annulation around the body just be- 

 hind the neck, which is followed by other similar rings at regular distances 

 throughout the length of the body, to the number of about sixteen. A narrow 

 median dorsal white line, commencing at the head, and two lateral ones, one 

 on each side, communicating at the neck, also extend throughout. Length, 3 

 inches ; breadth, at the middle, 0.08 inch. On weedy sand in the circumlit- 

 toral zone. 



Hab. Cape of Good Hope, at Simon's Bay. 



25. PoiiiA RHOMBoiDALis. Couvcx, largest anteriorly, of a pale reddish color, 

 with darker sub-margined longitudinal stripes. Head narrower than the body, 

 rounded in front ; neck slightly marked. Eyes in four clusters ; with four ocelli 

 in each cluster, arranged at the angles of a diamond-shaped area. The clusters 

 of the posterior pair are much the smaller, and are placed in the dark spots 

 forming the commencement of the longitudinal stripes. Length, 1 inch : breadth, 

 0.05 inch. Found in the littoral zone. 



Hab. Australia, at Port Jackson. 



26. PoLiA GRiSEA. Elongated, subcylindrical, of a grey color; head distinct, 

 subtriangular, much narrower than the body, and separated from it by a well- 

 marked neck. Eyes in four clusters ; two irregular rows on each side of the 

 head to the number of twenty more ; while on each side of the neck thero is an 

 elongated, oblique, reddish spot, with two or three ocelli along its outer edge. 

 Length, 0.8 inch. Found on sand-flats in the littoral zone. 



Hab. Coast of Virginia, at Norfolk. 



27. Tetrastemma insicum. Minute, slender, convex, broadest behind the 

 middle ; head with the eyes distinct, and with a lateral fold between the ante- 

 rior and posterior pairs, and one also behind the posterior pair. Color pale- 

 brownish. Length, 0.4 inch ; breadth, 0.025 inch. On weedy sand in the 

 circumlittoral zone. 



Hab. Cape of Good Hope, at Simon's Bay. 



28. Meckelia olivacea. Slender, convex above, especially anteriorly where 

 is also the greatest breadth ; head with a longitudinal slit which extends far 



1* 



