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 Astrjeidae proper, such as Cy- 

 phastra^a 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 Oculinidas proper and the 

 other among the Stylophorina?, whilst in reality the two genera can- 

 not be separated by any other characters. 



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

 enough either to the Oculinidaj or the Astranda3 to warrant their 

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

 the present to leave it as a small intermediate family. 



MADRACIS PouRT. 



Matlracl-i M.-Kdw. & H. 

 Axohelia ISI-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, Axohdia myiiader, 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 ctenenchyma, 

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

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

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

 pletely as in the true Oculinida^. The younger parts of Madracis 

 decactis show the space between the calicles proper and the mural 

 ridge occupied liy large vesicular spaces, which afterwards become 

 gradually filled up. 



I propose to retain the name Madi\acis 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 figui'ed in the Annales des Sciences 



