MEMBRANIPORIDjE. 27 



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



Cellulis ovatis, quaclri costatis, costa infima media impari ; sulcis lougitudinaliter 

 striatulis sen obscure puuctatis ; orificio suborbiculari ; spinis tribus marginalibus. 



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

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

 spines. 



L. CATENA, S. W., 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 LepralicB, though the means by which it is exerted is very obscure. 



B. CRUSTACEA. 



Fam. IV. MEMBRANIPORID&. 



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

 zontalibus, quincuncialibus seu oppositis, contiguis composito. 



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

 cells horizontal, quincuncial, or opposite, series contiguous. 



FLUSTRA (pars), Linn. 



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



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



MEMBKANIPORID.E, 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. MEMBRANIPORA. 



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



2. LEPRALIA. 



