MEGAPORA. 171 



RANGE OF VARIATION. Only two or three specimens have 

 been examined ; and they exhibit very little variation, 

 except in the size of the nodules, which constitute so 

 striking a feature of the species. 



HABITAT. Shells from about 30 fathoms and from 

 deeper water. 



LOCALITIES. Off the coast of Antrim (Hyndman) 1 : South 

 Devon, off Brixham (T. H.). 



This species is at once distinguished from M. Rosselii, 

 perhaps its nearest ally, by the much smaller size and 

 oval form of the cell, the continuous and very slightly 

 granular margin, and the large and conspicuous inter- 

 cellular bosses or nodules. 



Genus MEGAPORA, Hincks. 



Der. From /iryas, large, and iropos, an opening. 



LEPRALIA (part.), Busk. 



MEGAPOHA, Hincks, Ann. N. H. 1877. 



GENERIC CHARACTER. ZOARIUM incrusting. ZOCECIA 

 with a depressed area in front, surrounded by a raised 

 margin, and partially closed in by a calcareous lamina ; 

 aperture trifoliate, the lower portion filled in by a homy 

 plate, on which the opercular valve works. 



THIS genus is instituted for the remarkable form de- 

 scribed by Busk as Lepralia ringens. It exhibits many 

 points of resemblance to some of the Membranipora (e. g. 

 M. Flemingii), and should certainly, I think, be included 

 in the present family. 



It holds its separate place and name by virtue of the 

 peculiar structure of the aperture. 



