NORTHUMBERLAND AND DURHAM. 147 



on each side near the top, one of wliich is usually covered 

 by the ovicaj^sule. Ovicajisule subcylindrical, smooth, 

 with a strong rib above the margin, and surmounted by 

 a conical avicularium. 



Flustra unicornis^ Flem. Brit. Anim., 536. 

 Memhranipoi^a memhranacea, Johns. Brit. Zooph., 



328 (part)? 

 Lepralia squama, Daly. Rare and Rem. Anim. Scot., 

 V. 2, p. 79, t. XXV., f. 14, 15. 

 On old bivalve shells, on stones, and on the test of Ascidia 

 sordida ; frequent. 

 Dr. Fleming's description of his F. unicornis agrees so well 

 with this species that I have no hesitation in adopting the 

 name, although, as is the case in most of the old descriptions of 

 this difficult genus, more than one species may have been in- 

 cluded under it. M. unicornis has the cells larger, stouter, and 

 more regularly oval than in the two last, and wants the inner 

 sub-corneous expansion of M. Flemingii. But the best dis- 

 tinguishing character is found in the ovicapsules, which, in this 

 species, are smooth (never frosted), have a strong rib just above 

 the margin, and are surmounted by a conical avicularium, 

 giving the whole the appearance of a Phrygian bonnet. When 

 the ovicapsule is absent, the avicularium appears as " a blunt, 

 hollow, conical process " above the cell. I have never seen an 

 avicularium developed in any other position in this species, as 

 is usual in its congeners. 



36. FLUSTKELLA, Grai/. 

 1. F. HiSPiDA, Fah. 



Flustra hispida, Johns. Brit. Zooph., 3G3, t. Ixvi., f. 5. 

 Flustrella Idspida, Grray, Radiated Anim. Brit. Mus., 

 108. 

 On Fucus serratus and other sea-weeds between tide-marks, 

 and occasionally on stones; common. 



