18 VERRILL, SYNOPSIS OF 



smallest consistent with their structure (Antvpathes, &c.) 

 and several others in which it is constantly twelve, but the 

 smallest number of tentacles observed in any well formed 

 individual of Madreporaria is twelve, as in Pontes, Madre- 

 pora, &c. 



The bilateral arrangement of parts is very well brought 

 out in each order, but, perhaps, as strongly as in any in 

 some Actinia in which the mouth is oblong and furnished 

 with peculiar tubercles in pairs on the sides, but differing 

 entirely at its opposite ends {Peachia, Siphonactinia, &c.). 

 In other cases one of the tentacles in the median plane is 

 much longer or differs in color and structure from the rest. 



The character of being simple or compound, which has 

 been referred to by some authors as indicating grade, seems 

 to be of little or no importance. In each of the two orders 

 under consideration, both simple and compound species 

 occur, and sometimes within the same natural family, 

 while many that are simple when fully grown, doubtless in- 

 crease while young by fissiparity or gemmation. There 

 seems at least to be no reason to suppose that a compound 

 attached Madrepora is so highly organized as the freely 

 moving Actinia, which has a far more highly complicated 

 structure and more diversified functions. 



In the present article, however, it has been found more 

 convenient, on account of the arrangement of the plates, to 

 take up the Actinaria after the Madreporaria. 



OEDEE, MADEEPOEAEIA Edw. and Haime, restricted. 



This division I have^ raised to the rank of an order, thus 

 making it parallel with Alcyonaria, long since separated 

 by Milne Edwards, Blainville, and others, as well as with 

 Actinaria, which has hitherto been united with it, either as 

 a suborder, or more intunately combined, so that sometimes, 

 even in recent works, families of the two groups are placed, 

 in close proximity within the same tribe. 



The group itself, however, has been recognized as a natu- 

 ral one by several authors, and the same limits have been 

 assigned to it as I have given, with the exception of some 



