MADRACIS. 27 



the latter. This relationship is based chiefly on the density of the 

 caenenchyma, but this is a very variable character, and some genera 

 left by the same authors among the Astraeidae proper, such as Cv- 

 phastnva for instance, have it just as compact as Stylophora, though 

 less abundant. The reliance on this character alone has induced 

 Milne-Edwards and Haime to establish the two genera Axohelia and 

 Madracis, and to place the one among the Oculinidaa proper anil the 

 other among the Stylophorinae, whilst in reality the two genera can- 

 in it be separated by any other characters. 



The group, on the whole, does not appear to be allied closely 

 enough either to the Oculinidae or the Astraeidae to warrant their 

 combination with the one or the other as a subfamily. It is better for 

 the present to leave it as a small intermediate family. 



MADRACIS Poukt. 



Madracis M.-Edw. & H. 

 Axohelia M.-Edw. & H. 



A comparison of several representatives of the genus Madracis with 

 an Axohelia from the West Indies, very closely allied to, if not 

 identical with. Axohelia myriaster, M.-Edw. & H., has convinced me 

 that the two genera cannot be separated, and much less placed in 

 different subfamilies. The only difference is in the caenenchyma, 

 more abundant and compact in the one than in the other; but this 

 is a difference only in degree, for in both forms the caenenchyma 

 becomes solid, but the interseptal chambers do not fill up com- 

 pletely as in the true Oculinidae. The younger parts of Madracis 

 decadis show the space between the calicles proper and the mural 

 ridge occupied by large vesicular spaces, which afterwards become 

 gradually filled up. 



I propose to retain the name Madracis for the two genera com- 

 bined. 



Madracis asperula M.-Edw. & H. 



Plate VII, fig. 4. 



The specimens which we refer to this species are in general a 

 little slenderer than the one figured in the Annates des Sciences 



