﻿GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 471 



almost flat in others, and more or less largely gibbous in all; inter- 

 calicular groove very decided. Corallites usually very large, and 

 never very small. Wall very delicate and indistinct; costae small; 

 columella large. Septa variable in cyclical arrangement, the larger 

 excessively developed at the wall and linear within. Endotheca 

 abundant, but not in excess, vesicular. Exotheca not well devel- 

 oped, but decided and plentiful. Calices invariably found as casts. 

 Impressions prove them to have been shallow. Coenenchyma well 

 developed. 



''These characters, common to many forms, are more or less varied 

 in intensity in difl^erent specimens. The septal number varies in 

 individuals of the same corallum, in one series of forms, to a remarka- 

 ble extent, although the corallites thus differing are nearly equal 

 in diameter, and are nearly, if not quite, as advanced in development. 

 In other forms it is fixed to four cycles in six systems; whilst in 

 some there are three cycles in some S3^stems, and only two in others, 

 the corallum being large. 



''The form which I consider t3^pical of the species has four perfect 

 cycles in six systems; but in some corallites the rudimentary sixth 

 and seventh orders of a fifth cycle exist. The specific character- 

 istics — the thick and great development of the septal laminae at 

 their wall end, and the more or less linear, but entire, conditions of 

 their internal parts — are seen in all these forms, in the primary, 

 secondary, and tertiary septa, according to the relative septal arrange- 

 ments. In some corallites with a low septal number, the primary 

 septa alone are thus characterized; and as the higher cycles are 

 seen, so the secondary and tertiary septa become enlarged and resem- 

 ble the primary. The septa of the higher orders are either linear 

 throughout or slightly enlarged at the wall; and as they approach 

 the tertiary or quaternary, as the case may be, they are seen to 

 become more equal to them in size. In examining these forms 

 allowance must be made for their fossil condition; and attention 

 must be given, in examining transverse sections of corallites, that 

 they are quite at right angles to the corallite, for any obliquity will, 

 of course, diminish the peculiar spear-shape or mace-shape of the 

 septa, and render them more like a paddle, or a leaf with the stalk 

 attached. 



"The tendency of the higher orders of septa to become linear 

 throughout, or to be less decidedly large at one end and thin else- 

 where — that is, more or less uniformly thick, but in a less degree 

 than is usual at the wall — is seen throughout the species; and in a 

 gigantic variety, where the fully developed corallites have 12 or 14 

 septa in every system, the whole of the septa are less decidedly 

 thick at the wall, and are either more or less so throughout, or present 

 the usual form of the septa in a modified degree. 



37149— 19— Bull. 103 19 



