INTRODUCTION-. 



13 



Epitheca. An external calcareous crust, deposited upon some 

 zoaria. In most cases it consists of a compact layer upon the 

 basal portions of the zoaria, as in Apsendesia. But in others it 

 consists only of a thin irregular deposit, filling up the depressions 

 between zocecia, which appear to be immersed, as in some species 

 of Berenice a. 



The transverse ridges which cross some zooecia (as Berenicea) 

 are probably epithecal growths. 



Intervesicular tissue. Cellular calcareous tissue, which separates 

 the zocecia in some genera, such as Fistulipora. 



Zoarial lamina. The supporting layer present in foliaceous 

 genera such as Diastopora (Fig. 3). It is the "lame gerrninale " 



FIG. 3. Longitudinal section through a frond of Diastopora, showing zoarial 

 lamina. From Great Oolite, Bath. D. 2246. 



of D'Orbigny, which he described in Stellocavea. The term lamina 

 cannot be used without a qualifying adjective, as alone it has 

 a different meaning in Membraniporidae. Median lamina is used by 

 Ulrich, but this can hardly be applied to unilaminate zoaria, such, 

 as Diastopora lamourouzi, M. Edw. 



Lunar ium. Crescentic projecting plates, below the aperture, 

 formed by the thickening of the peristome on the side opposite 

 the anus, as in Chilopora. 



Terminology of Apertures. 



" Orifice," The oral opening of the digestive tubes; it is there- 

 fore the mouth of the zooid. 



Aperture. The opening or mouth of the zooscium. 



