132 Transactions. — Zoology. 



Family ANUE^AD^E. 



Genus Notholca, Gosse. 



Generic characteristics : Lorica ovate, truncate, and six- 

 spined in front, sometimes produced behind, of two spoon-like 

 plates united laterally ; no hind spines. Dorsal surface 

 marked longitudinally with alternate ridges and furrows ; 

 expelled egg not usually carried. Lacustrine and marine. 



XVI. Notholca regularis,'^' sp. nov. Plate XI., figs, xvi., xvi.a. 



Specific characters : Body oval in outline, with a slight 

 contraction in the middle. The six spines on the occipital 

 edge are nearly all exactly the same size. Ventral plate 

 slightly shorter than the dorsal one. An open cleft between 

 the two posteriorly, but they are commensurate occipitally 

 and laterally. Semi-marine. 



Colour : There is a round red eye of medium size, and a 

 very large russet salmon-coloured egg of more than half the 

 bulk of the whole body. The body is depressed, and looked at 

 from above has the appearance of a tolerably regular oval, 

 slightly broader behind. There is no foot. The head is not 

 sharply marked off from the body, but is seen to have a defi- 

 nite size by its retractability. It continues forwards the 

 regular shape of the body. The ciliary wreath is single, and 

 fringes the corona, on which there are also three prominent 

 setigerous prominences. The centre of these is the narrowest, 

 and slightly the longest. The lorica is entire, depressed, flat 

 below, arched dorsally. The upper and lower valves are not 

 exactly applied posteriorly, but leave an open cleft. Its 

 anterior margin is ornamented with six sharp and graceful 

 spines ; four of these spines are dorsal and two lateral. The 

 median cleft between the two inner spmes is the deepest. 

 The whole lorica is of hyaline transparency. The mouth is 

 terminal and central. The mastax is of the malleate type, 

 situated at about the junction of the head and body. The 

 alimentary canal passes round to the left side of the body, 

 then bends centralwards again, and ends in the posteriorly 

 terminal cloaca. No especial muscles were noticed, except 

 some ceaselessly active ones in the walls of the rectum, which 

 is always undergoing opening and closing movements like 

 those of a heart. The rectum is attached by muscular bands 

 to the lorica. The only sense-organ is the round eye set in 

 about the centre of the head. No definite parts of the excre- 

 tory system were noticed, except the contractile vesicle in 



* Evidently closely akin to N. jugosa (Gosse, Jour. Roy. Mic. Soc, 

 1887, p. 1), but differing somewhat in general shape, ciliated prominences, 

 position of eye, and absence of furrows. 



