ASCIDIA PELLUC1DA. 143 



extended disc. Bran-cliial tijx'rtnre terminal, wide and 

 tubular ; anal on a short tube a little way down the 

 side, curving upwards; ocelli conspicuous, red. 7Vx/ 

 smooth, coriaceous, and perfectly transparent. M<tntl< j 

 small in proportion to the test, yellowish white, in- 

 clined to red on the lower parts. 



LriKjth half an inch. 



Hnl>. Under stones within tide-marks. 



ENGLAND. Cullei^coats, Nor thumb., rare (Hancock). 

 [Falmouth, Cornwall (Codes, 1849).] 

 WALES. Meiiai Straits (Alder). 

 IRELAND. Killinny, Galway (Thompson). 

 l. Alder and Hancock, 1848. 



The vascular ramifications of the test (PL XVI, fig. 

 8) are not very conspicuous ; and the mantle is delicate 

 and only feebly supplied with muscular fibres. 



The branchial sac (PL XVIII, fig. 12) is rather wide, 

 but does not reach to the lower border of the visceral 

 mass ; it is simple, not undulated or plicated ; the 

 primary vessels are pretty equal in size, and are placed 

 rather near to each other ; consequently the stomata 

 are shorter than usual, and have the extremities 

 rounded. The longitudinal bars do not bear papillae ; 

 but in their place, at the intersection, there is a stoutish 

 nodule or boss, which gives support to an almost 

 obsolete papillary membrane. The oral lamina, which 

 is not particularly wide, has the right side ribbed ; and 

 the branchial tubercle in front of it is a simple loop 

 open above. The tentacular filaments are numerous, 

 long, and slender, but vary in length ; they are placed 

 close together in a single line. 



A. i>fll K ri<l ti is a very distinct species, and is readily 

 determined both by its external and internal characters. 

 The ovate or subtriangular form, the shortness of the 

 branchial sac, with the simple structure of the aerating 

 surface, and the deficiency of papillas on the longi- 

 tudinal bars, at once distinguish it. 



