372 Observations upon Stenopora fibrosa, etc. 



that the whole grew contemporaneously, and that the struggles for space 

 of the vigorous, rapidly es oanding young polype, interfered with the 

 outline of the walls of the fiv 1-grown animal, which necessarily possessed, 

 on account of its lateral enlargement having ceased, no power to resist 

 such encroachments. From the mode of development having been thus 

 wholly interstitial, it is inferred that the exterior surfaces of adjacent 

 walls must naturally and easily separate. It- is further inferred, that 

 the polypes, at the superior boundary of the coral mass, had no common 

 connection, but were perfectly circumscribed and separated. 



The essential manner of developing additional tubes in Cheietes was, 

 however, by a subdivision within the area of the parent. On exam- 

 ining transverse sections, particularly those in which the coral is but 

 slightly coated with infiltered matter, a plate will be frequently seen 

 projecting from one or more sides, and by extending the research, 

 similar laminee will be found to range quite across, effecting either 

 a simple subdivision into two areas, or a complex one into three or 

 even four. These intersected spaces are easily distinguished by the 

 plates springing from sides, and not angles. Again, in a vertical 

 section of such specimens, thin interrupted laminae will be readily 

 detected, ranging perpendicularly within many of the tubes. They 

 are not usually continuous for any distance, but they perfectly agree 

 in their nature with the plates just noticed, and the want of persistence 

 may be rightly assigned to the perishable tendency of the coral. 

 Cases, however, were observed of plates which extended without 

 interruption, and probably from their first development for more than 

 an inch. In such examples, the walls of the original tube ranged 

 regularly upward, but svith a slight divergence, and the introduced 

 laminffi, at first not quite medial, gradually assumed that position. 

 From this plan of producing additional tubes, it is presumed that 

 there could be no natural tendency in the component structure of the 

 walls to divide into two plates, as in Favosites ; and, further, that the 

 polypes, by which a mass of tubes was formed, had a community of 

 existence, and were united at the outer boundary of the coral in one 

 animal layer. 



Based on these imperfectly explained structures, the following pro- 

 visional generic charactei's are proposed : 



A polymorphous polypidom, formed of tubes, closely aggregated 

 and transversed by diaphragms; walls inseparable; additional tubes 

 produced by subdivisions, within the ^rea of the parent tube, or by 

 extensions of the polype along the margin of the coral mass. 



To suggest grounds for specific distinctions in fossil corals, of so sim- 

 ple a composition, is extremely difficult, especially when characters 



