24 FREDERICK W. SARDESON 



tabulated, thin-walled, polygonal cells. Chcetetes has compara- 

 tively lighter colored, probably more calcareous walls. Its cells 

 increase only by fission, while intermural "budding" obtains in 

 Mouotrypa. It is said, however, that fission occurs rarely in 

 Monticuliporoidea, which leaves a difference in degree only 

 between these two. Chcetetes is extinct, but is referable only as a 

 coral. It indicates that the Monotrypa, Moiiticulipora, etc., are 

 corals; but that the family Chcetetidce should contain Montiadipora 

 seems doubtful when Fistulipora is placed in a family of its own. 1 

 Certainly Prasopora does not belong in both. 



Fistulipora, which is the extreme form of Trepostome as com- 

 pared to Mo?iotrypa, is the very one most approaching the Recent 

 coral, Heliopora, which, as shown by Mosely, is an Alcyonarian, 

 with a true tabulate skeletal structure. Heliopora has the larger 

 cells, but like Fistulipora has autocells among mesopores, called 

 siphonopores. The autocells increase by " ccenenchymal gem- 

 mation," i. e., a young autocell arises among siphonopores, dis- 

 placing several. Siphonopores and mesopores are alike. Also, 

 in the mature region of Heliopora, the walls thicken and a wart- 

 like projection stands generally at the siphonopore angle and 

 twelve of them surround the autocell. Structurally the warts 

 are similar to "acanthopores," but the wall of Heliopora is highly 

 calcareous, and in thin section one sees primarily the crystal- 

 line structure radiating from the normal line or center, while 

 the Monticuliporoid wall, being apparently less calcareous, 

 shows the organic lamination, and the acanthopores have con- 

 centric structure. The difference is referable to the degree of 

 calcareous deposit in which all corals differ. The warts on 

 Heliopora are due to transverse canals between zooids swel- 

 ling the cortex unevenly. Acanthopores might well be of 

 like origin, and if so they indicate a canal system like that in 

 Alcyonaria. 



It has not been clearly enough understood that Mosely 2 

 demonstrated the Heliopora to have no mesenterial septa, but 

 that twelve vertical ribs in each autocell are pseudosepta ; and 



1 Eastman, op. cit., pp. 102, 103. 2 Challenger Report. 



