2 BRITISH TDNICATA. 



Section 1. With common excretory orifices. 



Genus 14. POLYCLINUM Savigny, 1816. 



Polyclinum SAVIGNY Mem. Anim. sans Vert. pt. 2 [1816], 

 p. 188; [LAMOUEOUX Exp. metli. Polyp. (1821), p. 75;] 

 MILNE EDWARDS Obs. Ascidies comp. [1841],* p. 76, [in 

 Mem. Acad. Sci. Inst. France, XV11I (1842), "p. 292;] 

 FORBES & HANLEY Brit. Moll. I [1848], p. 14; GOSSE 

 Man. Marine Zool. II [1856], p. 32; WOODWARD Man. 

 Moll. [pt. 3 (1856)], p. 342; H. & A. ADAMS Gen. Recent 

 Moll. II [1858], p. 599. 



Colon)/ [gelatinous or cartilaginous,] polymorphous, 

 generally more or less rounded, [usually] sessile, com- 

 posed of several radiating, [often] irregular systems, 

 each with a common excretory orifice. Individuals 

 [elongated,] varying in number in each system, and 

 placed at unequal distances from their common centres. 

 Branchial aperture with six salient lobes; atrial aperture 

 opening horizontally, with an even rim and a languet 

 above projecting into the common cloacal cavity. 

 Thorax cylindrical ; branchial sac [rather largely 

 developed,] with papillae. Abdomen smaller than the 

 thorax, pedunculated. Post-abdomen attached by a 

 peduncle arising from the side of the abdomen, slender 

 and much elongated. The thorax, abdomen, and post- 

 abdomen each occupying a separate cell. 



It is extremely difficult to extract the individuals of 

 this genus entire, on account of each of the three 

 portions into which they are divided occupying a 

 separate cell in the common mass. 



1. Polyclinum aurantium Milne Edwards. 



(Plate LI, figs. 1-5 ; Plate LVI, fig. 1 ; and figs. 88 



and 89 in text.) 



Polyclinum aurantium MILNE EDWARDS Obs. Ascidies comp. 

 [1841], p. 76, [in Mem. Acad. Sci. Inst. France, XVIII 



* The separate (or author's) copies bear this date, having apparently 

 been issued before the Memoires of the Academie in which the work appeared. 

 As Alder & Hancock quote the pages of these copies, they are retained. 



