Polyzoa of Queen Charlotte Islands. 7 



dark-coloured, semicircular mandible (or modified oral valve). 

 It represents one of the earliest stages in the developmental 

 history of this appendage*. 



It may be a question, perhaps, whether C. mandihulata 

 should not be regarded as a " form " of C . fistula sa ; but it 

 has much the same kind of claim to specific rank as C. sin- 

 ■uosa. After all, these systematic distinctions are only meant 

 to mark the developmental steps. 



Family Membraniporidse. 



Group a {Flustrid^). 



Flustea, Linneeus. 



Flustra memhranaceo-truncata^ Smitt. 



Virago Sound, 8-15 fms, [North Sea, Arctic Seas, 

 common,] 



Group h. 



Membranipora, De Blainville. 



Memhranipora unicornis^ Fleming. 



Houston Stewart Channel, 8-20 fms. ; very fine. [Spitz- 

 bergen, Greenland, Nova Zembla, Labrador, Britain (north- 

 east.] 



Membranipora Rosselu, Audouin. 



Houston Stewart Channel, on shells, not uncommon. 

 [Britain, Algiers, Adriatic] 



Memhranipora tenuirostris, Hincks. 



Off Cumshewa Harbour ; Houston Stewart Channel. 

 [Mediterranean j Madeira.] 



Memhranipora horrida^ Hincks. 



Houston Stewart Channel, 8-10 fms. ; off Cumshewa Har- 

 bour. Abundant and very fine, forming very large, reddish- 

 brown patches on shells. [California ; Vancouver Island.] 



Memhranipora patula, Hincks. 



Virago Sound ; Houston Stewart Channel, &c., very com- 

 mon and of luxuriant growth. [California.] 



* We have a very similar form in CeUaria husuta, MacGillivraj, and 

 Membranipora longicornis, mihi. See * History of British Marine Polyzoa,' 

 Introduction, p. Ixviii, fig. xxx. 



