300 TABULATE CORALS. 



non-tabulate tube, bounded by very thick dense walls. In 

 some cases, also, the central tube of the spines seems to be 

 continued to the actual surface, though I have failed to detect 

 openings in the surface-columns. I have, however, no doubt 

 but that the surface-columns are primitively perforated, and 

 that the spines are, therefore, genuine corallites, though of a 

 peculiar kind. The forms to which Dekayia shows the greatest 

 affinity are those like Montic2ilipora {Hetcrotiypa) moitilifoinnis, 

 Nich., but in these the spiniform corallites are much more ex- 

 tensively developed. I must, however, defer further considera- 

 tion of this subject till I am able to separately discuss the very 

 remarkable features exhibited by the spines of various of the 

 Monticuliporoids, as well as of certain species of Stenopora. 



FormatioJi and Locality. — Rare in the Cincinnati group, 

 Cincinnati, Ohio. 



Sub-genus Constellaria, Dana, 1846. 



(Zooph., p. 537, 1846.) 



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



This section includes forms which, in many respects, are 

 very nearly allied to Fistulipora, 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 sub-genus. The corallum in ConstellatHa is obviously 

 and conspicuously dimorphic, the most striking of its features 

 being the existence of a series of close-set, star-shaped, de- 

 pressed areas (" maculae "), which are occupied by the smaller 

 tubes, and which are surrounded each by a radiating circle of 

 short elevated ridges carrying large tubes (PI. XIV., fig. 5). 

 The large tubes also occupy, mainly or wholly, the spaces be- 

 tween the star-shaped monticules, and each is oval or circular 



