XIV ZOANTHARIA MADREPORARIA 40 1 



new directive mesenteries arise. In some cases very large corals 

 are formed, and, if our conception is correct, these must be 

 regarded, not as a colony of zooids, but as a single individual 

 zooid divided into a considerable number of incompletely sepa- 

 rated parts. Among the well-known genera belonging to this 

 group are EujpTiyllia, Mussa, Meandrina, Coeloria, Favia, and 

 Goniastraea. 



In such genera as JEuphyllia the parts of the colony become 

 separated by deep grooves, and have the superficial appearance of 

 being distinct individuals ; but in the Brain-coral Coeloria and 

 others the surface of the coral presents a series of more or less 

 bent or curved grooves, each with a row of slit-shaped mouths 

 and bordered by rows of tentacles. 



A number of genera of solitary corals united in the sub-family 

 Trochosmiliacea are generally included in the family Astraeidae. 

 The study of their skeletal characters has suggested^ that they 

 are more closely allied to the Turbinoliidae. The principal genera 

 thus transferred would be Trochosmilia, Placostnilia, Parasmilia, 

 and Asterosmilia. As these genera and their allies are nearly 

 all extinct, and nothing is known of the structure of the living 

 zooids, their removal from the Astraeidae may be regarded as 

 not fully justified. 



Fam. 4. Pocilloporidae. — The general anatomy of the zooids 

 of this family of corals has some resemblance to that of the 

 Entocnemaria, and it is possible that they will eventually find a 

 place in our classification near to, if not actually within that 

 group. The fact, however, that the skeleton is imperforate is 

 sufficient for the present to justify the inclusion of the family 

 in the section Aporosa. There are but two genera at present 

 known, and in both of them the zooids have twelve tentacles, 

 twelve mesenteries, and only two mesenterial filaments. The 

 zooids are connected together by an elaborate system of canals 

 running in the superficial coenosarc. The calices are bilaterally 

 symmetrical, and in Seriatopora the septa which are parallel 

 with the axis of the branch are united in the centre of the 

 calyx, and are very much larger than the others, as in Madrepora. 

 In all these characters the family shows affinities with the 

 Entocnemaria. In the characters of the skeleton, which is 

 imperforate and tabulate, the affinities are rather with the 

 ' M. Ogilvie, Trans. Roy. Soc. olx.^xvii. B. 1896. 



VOL. I 2d 



