MEMBRANIPOEID^. 27 



2. A. CATENA, S. W. (sp.) PI. VII, fig. 7. 



Cellulis ovatis, quadri costatis, costa, infima media imparl; sulcis loiigitudinaliter 

 striatulis seu obscure puiictatis ; orificio suborbiculari ; spinis tribus marginalibus. 



Cells ovate, with four costae on each side and a single median one below ; sulci 

 longitudinally striate, or obscurely punctate ; orifice suborbicular ; three marginal 

 spines. 



L. CATENA, /S. TV., 1. c, p. 



Habitat. — Cor. Crag, Sutton, 8. W., on the inside of a small bivalve. 



This species appears to possess, in a remarkable degree, the power of excavating or 

 eroding the surface of the shell upon which it grows, a property common to several 

 other Lepralia, though the means by which it is exerted is very obscure. 



B. Crustacea, 

 Fam. IV. MEMBBANIPOMBM. 



Polyzoario membranaceo-calcareo seu calcareo, incrustante, adnato, cellulis hori- 

 zontalibus, quincuncialibus seu oppositis, contiguis composite. 



Character. — Polyzoarium membranaceo-calcareous or calcareous, adnate, encrusting ; 

 cells horizontal, quincuncial, or opposite, series contiguous. 



Flustra (pars), Linn. 



FLUSTRADiE (pars), Gray, Cat. B. M., 145. 



Celleporidje (pars), Johnston, Brit. Zoophyt,, 2d ed., p. 263. 



Membraniporii)^, Busk, B. M. Cat., p. ii, p. 56. 



SYNOPSIS OF GENERA. 



(a) Cells more or less open or membranaceous in front, with raised margins ; growth 

 indefinite. 



1. Membbanipora. 



(i) Cells closed in front ; contiguous ; growth usually circumscribed. 



2. Lepralia. 



