MEMBRANIPORA SPINIFERA. 149 



MeMBRANIPORA SPINIFERA, JohustOll. 



Plate XIX. figs. 1, a, b, c. 



Flustra SPINIFERA, Johist. Newc. N.H.S. Trans, ii. 266, pi. ix. fig. 6. 



? Flustra lineata (part.), Johnsf. B. Z. ed. 2, 349. 



MeiMbranipora SPINIFERA, Aider, North. Cat., Trans. Tynes. Field Club, iii. 

 143, pi. viii. fig. 2: Hiiicks, Dev. Cat., Ann. N. H. ser. 3, 

 ix. 29 [not M. spinifera of Smitt, CEtVers. K. Vet.-Ak. Forh. 

 1867, 366 & 411, pi. xx. fig. 32*]. 



Zocecia elongate-oval, contiguous, arranged in lines ; the 

 margin with about 14-16 tall and stout spines, two of 

 them at the very top of the cell, the second pair erect 

 and very large, the rest bending inwards. Avicularia 

 pedicellate, borne on a short and slender stem, which 

 tapers downwards, developed on the cells, outside the 

 row of spines ; mandible acute and directed upwards. 

 Ocecia shallow, smooth, with a rib across the front. 



Colonies forming rather large, circular, brownish patches. 



Range of Variation. I have only noticed slight differ- 

 ences in the size of the cells and the number of the spines. 

 The avicularia are sometimes very sparingly produced, or 

 at least are present in very small numbers. It is very 

 probable that their absence in such cases may often be due 

 to accidental causes ; for the pedicle by which they are 

 connected with the cell is much attenuated below, and 

 they must be easily detached from their place. On some 

 specimens almost every cell is furnished with one of these 

 curious appendages. 



Habitat. Chiefly on stones, between tide-marks ; 

 also on Laminaria and on shells, &c., from moderate 

 depths. 



Localities. Northumberland and Durham, '^ on the 



* This is the M. cymh(Bformis, mihi, an Arctic and North-American form. 

 Vide a paper bv the author in the Annals & Mag. N. H. for Jan. 1>!77, 

 p. 110. 



