504 TLUSTRELLID^. 



Doubtful Species. 



Alcyonidium radiatum^ Alder, MS. 



In his Report ou Shetland Polyzoa, Norman mentions a 

 species of Alcyonidium which he had found between tide- 

 marks in the Out Skerries, and to which Mr. Alder had 

 given the above (manuscript) name. No description of 

 it has been published. 



Family II. — Flustrellidae. 

 Halcyonelle^ (part.), Smitt. 



ZocECiA immersed in a gelatinous crust ; orifice bilabiate. 

 LarvvE furnished with a bivalve shell. 



Genus FLUSTRELLA, Gray. 



Der. Dim. of Flustra, the sea-mat. 



Flustrella, Gray, B.M. Cat. Eadiata : R^dfern : Alder : &c. 

 Flustra (part.), Fleming : Blaiuville : Johnston : Couch : Hincks : &c. 

 Alcyonidium (part.), Smitt. 

 {Not Flustrella of D'Orbigny.) 



Generic Character. — Zocecia immersed, the orifice 

 bilabiate, ivith a movable lip, which acts as an operculum. 

 ZoARiuM a gelatinous crust. 



This genus is distinguished from Alcyonidium, with 

 which it agrees in most points, by an important difference 

 ill the structure of the orifice. It is furnished with a 



