SIDNYUM. 13 



tracted into a very long and linear tail, as it may be called, in 

 which, when compressed, we perceive a dark intestine-like mark, 

 mottled with darker and lighter shades on each side, and a clear 

 space between them ; but I cannot trace any distinct termi- 

 nation of these organs (which are the ovaries) in the branchial 

 sac, although the shadings at the base of this part indicate the 

 existence and situation of some distinct organs. This species has 

 a great resemblance to Aplidium effusum of Savigny, but I cannot 

 consider them identical. — Hab., Berwick Bay, in deep water." — 

 Johnston. 



In the twenty-sixth volume of the "Edinburgh New Phi- 

 losophical Journal," (p. 152,) Sir John Dalyell gives an 

 account of a compound Ascidian, from the Frith of Forth, 

 under the name of " Aplidium verrucosum.'''' He describes 

 it as " a gelatinous -looking, but solid, compact substance, 

 which, being suspended by silk threads in a jar of sea- water, 

 jiroved of an olive-green colour, and approached the form of 

 an irregular parallelopiped above three inches long, and 

 equalling perhaps three cubical inches of solid contents. 

 The whole mass covered with very low prominences, almost 

 even with the surface. In a short time the prominences 

 developed as a profusion of short, projecting, cylindrical 

 orifices, each fashioned as a lip, with a smooth, even edge, 

 wherein were attracted by a powerful current, and absorbed, 

 the neighbouring buoyant particles." 



SIDNYUM, Savigny. 



This genus was made known by Savigny in a note sup- 

 plementary to his memoir. He founded it for a British 

 Ascidian received from Dr. Leach, but did not figure the 

 species. It belongs to the uuistellated section of the tribe 

 " Polycliniens " in the arrangement of jNlihie-Edwards. 



The mass presents the appearance of a number of heads of 

 madrepore or cladocora, each formed of a simple cone truncated 

 and starred at the summit, rising from a common encrusting base, 



