2 5^ TABULATE CORALS. 



When we consider the structural characters of Heteropora, 

 as above briefly indicated, it cannot be denied that there is a 

 general resemblance between this type and the ancient Monti- 

 adipora and Fistidipora. Dr Lindstrom, in the memoir already 

 referred to, has further brought forward a considerable body of 

 evidence, which I shall more fully allude to hereafter, to prove 

 that the developmental history of Montictdipora shows it to be 

 a Poly soon. In the meanwhile, however, I am unable to admit 

 that we have sufficient evidence for the removal of Monticuli- 

 pora and its allies from the Actinozoa, and their transference 

 to the Polyzoa. So far as Heteropora is concerned, the genus 

 seems to be sufficiently separated from Motdicidipora by its 

 total absence of genuine tabulse in the cells themselves and its 

 (occasionally) perforated walls, together with the occurrence in 

 some forms of radiating septa in the interstitial tubes. On 

 the other hand, Monticrdipo7''a presents the closest possible 

 resemblance in most of its structural features to the ramose 

 Favositidcs, from which it can only be separated by the general 

 possession of two sets of corallites and the apparent absence 

 of mural pores. That the latter are true Actinozoa does not, 

 in my opinion, admit of doubt, and I think we must in the 

 meanwhile come to the same conclusion as regards Mouticidi- 

 pora itself and the closely-allied Fisttdipora, Constellaria, and 

 Prasopora. The three last of these types, and the great 

 majority of the forms usually included under the first name, 

 possess a corallum which is composed of two distinct sets of 

 corallites, a feature which at once reminds us of the Helio- 

 porida, and would lead us to suppose that the Montiadiporida; 

 are to be regarded as an ancient group oi Alcyonaria. More- 

 over, the different sets of corallites in these forms are not only 

 unlike in point of size, but the smaller tubes are almost in- 

 variably more closely tabulate than the larger tubes, this being 

 another feature in which they unmistakably approach the 

 HelioporidcE. In no known forms of Polyzoa, not even in 

 HeteropoTa, can a similar condition of parts be shown to exist, 

 and I am therefore of opinion that we are not justified, with 



