30 BRITISH TUNICATA. 



intermediate between Synoicum and Aplidium, and 

 only to be distinguished from the latter by the struc- 

 ture of the stomach ; the very slender and peduncu- 

 lated form of the ovary (post-abdomen)* giving it at 

 the same time some resemblance to Sigillina. 



The genus ought probably to be united to Aplidium. 



1. Sidnyum turbinatum Savigny. 



Sidni/um turbinatum SAVIGNY Mem. Anim. sans Vert. pt. 2 

 [1816], p. 239. 



Colony perfectly transparent [lobed, each lobe corre- 

 sponding to a system]. Individuals arranged in long, 

 narrow ellipses directed from the centre towards the 

 circumference. (Other characters as in the genus of 

 which this is the only species.) 



Dr. Fleming found what he was inclined to consider 

 8. turbinatum on the rocks of the Isle of May, and his 

 description of it in ' British Animals ' is compounded 

 of the characters of Savigny's genus and of those 

 of his own recent specimen. Professor Edward 

 Forbes, again, has adopted what we believe to be 

 another species as the Sidnyum turbinatinn of Savigny, 

 and has altered the generic character to suit it.f It is 

 only necessary, however, to pay a little attention to 

 Savigny's description to be convinced that our distin- 

 guished English naturalist was under a mistake, and 

 that his species, an individual of which he figures with 

 a branchial aperture of eight lobes, and a broad, un- 

 pedunculated post-abdomen (see ' Brit Moll.' PL B, 

 f. 2), cannot be the animal described by Savigny with 

 a branchial aperture of six lobes, and a pedunculated 

 post-abdomen dilated and filiform (mince comme unfit}. 

 Besides which Forbes' species has a single circular 



* Savigny had not detected in these animals the character of the circula- 

 tion and position of the heart, which is situated along with the ovary in 

 "the post-abdomen" of Milne Edwards. 



t [These species are here described under the names of Parascidia 

 Flemingii and P. Forbesii (pp. 19 and 20).] 



