388 ESCHARID^. 



Geographical Distribution. Mazatlan ; Adelaide 



(T.H.). 



The appearance of R. bispinosa is much altered by the 

 absence of the large oral avicularia. When present they 

 form a striking character, and add much to the pic- 

 turesqueness of a very remarkable species. The swelling 

 on which they are develojaed is clearly a modified cell; 

 and in an early stage of growth its foundations are 

 marked out in raised lines, just as the nascent zooecia are 

 outlined round the edge of the crust. The mode of its 

 formation from the first to the final stage may be studied 

 on the margin of any fresh and growing colony in which 

 it is present. 



Genus RETEPORA, Imperato. 



Der. From rete, a net, and Tropos. 



Mii.LEPOKA (part,.), Linuffius : Pallas : Ellis : &c. 



Eetepoba, Imperato {Betepora eschara marina) : Johnston : Biisk : D'Or- 



bigny : Smitt: &c. 

 Eetepoea (part.), Lamarck : Blainville : &c, 

 EsciiARA (part.), Smitt. 

 DiscoPOKA (part.), Smitt. 



Generic Character. — Zocecia disposed on the front 

 surface of mi erect and ramose zoarium, the branches of 

 which usually inosculate and form a reticulate expansion; 

 orifice semicircular or semielliptical, with a prominent 7'os- 

 trum on the lower margin, bearing an avicularium. Zoa- 

 rium adherent by means of an incrusting base, composed 

 in great part of aborted cells ; avicularia developed on both 

 the bach and front of the zoarium. 



The present genus, as originally constituted, was 

 founded solely on the reticulated condition of the zoa- 



