136 BRITISH TUNICATA. 



indebted for a great number of new forms of both the 

 simple and compound Tunicata. 



25. Ascidia affinis Alder & Hancock. 



(PI. XV, figs. 8 and 9 ; PL XVIII, fig. 9 ; PL XIX, 

 fig. 12 ; and fig. 3 in text.) 



[Ascidia affinis ALDER & HANCOCK in Ann. Nat. Hist. (4), 

 VI (1870), p. 361.] 



Sod]/ elongated, ovate, tapering upwards, semi- 

 transparent, dirty greenish white ; surface smooth or 

 only slightly wrinkled, echinated and somewhat rugose 

 towards the base and apertures. Ap<>riur<>* prominent, 

 large, tubular, longitudinally ridged, rugose or echi- 

 nated ; the branchial terminal, the anal a little way 

 down the ventral margin. Test semi-transparent, 

 thin, cartilaginous, of an obscure, pale, soiled greenish 

 white, smooth above and slightly roughened or echi- 

 nated towards the base and tubes. Mantle pale olive- 

 brown, almost colourless and transparent at the tubes, 

 which are well produced, wide, and strongly ribbed 

 longitudinally, both being directed upwards. Tfiitm-nlm- 

 Jiluiitfiifx numerous, moderately stout, alternately large 

 and small. Branchial *<><' minutely plicated, papillary 

 membrane with the free margin much thickened, but 

 very slightly produced. Orallamina wide, smooth, or 

 only slightly ribbed at the base, margin entire ; the 

 left oral appendages seven or eight, large, triangular, 

 denticulated, leaflets. 



L( 3 ii<~/t]t upwards of two inches. 



Halt. Shallow water. 



ENGLAND. Roach river, Essex (Baird). Isle of 

 Wight, dredged in an oyster-bed (Jeffreys). 



First record. Hancock, 1870; coll. Baird [1805 or 

 earlier]. 



This species was obtained in great abundance by 

 Dr. Baird when examining the state of Roach River, 

 Essex, to report on its suitableness for the maintenance 



