SUBDIVISIONS. 97 



validity of the genus Fistidipora, M'Coy, or in the question 

 how far the later Callopora of Hall is identical with this, I 

 need only add that the species of Fistulipora are mainly dis- 

 tinguished from the typical MonticJilipoi^(T by the relative 

 abundance of the small corallites of the colony. In all the 

 typical Fistuliporcs with which I am acquainted, it is the rule 

 that the large corallites are completely isolated from one 

 another by the small interstitial tubes ; and the latter are not 

 only more closely tabulate than the former, but have their 

 walls commonly obliterated by the anastomosis of their tabulae. 

 On the other hand, in all the true Monti at lip ores the large 

 corallites are, to some extent, in contact, and the tabulae of 

 the interstitial tubes do not become vesicular. At the same 

 time, it must be admitted that there are some species of Moii- 

 ticulipora which make a close approach in internal structure 

 to Fishilipoi'a, and that it is not always an easy matter to sep- 

 arate these two orenera. 



As regards its geological range, the typical species of Fistu- 

 lipora appear to belong to the Upper Silurian, Devonian, and 

 Carboniferous periods. 



(II.) CoNSTELLARTA, Dana, 1846. 



(Zooph., p. 537, 1S46.) 

 Sfellipora, Hall, Pal. N.Y., vol. i. p. 79, 1847. 



This section includes forms which, in many respects, are 

 very nearly allied to Fistiilipora, M'Coy, but which exhibit 

 some very peculiar features. Some of the structural peculiari- 

 ties of the type will require for their elucidation much more 

 extended investigation than I have as yet been able to bestow 

 upon them, and the following must be regarded as little more 

 than a general and provisional statement as to the characters 

 of the genus. The corallum in Constellaria is obviously and 

 conspicuously dimorphic, the most striking of its features being 

 the existence of a series of close-set, star-shaped, depressed 



