130 BULLETIN OF THE LABORATORIES 



anywhere a concave curvature took place it appeared strongest near- 

 est the bas^ of the coral on the side of the central gap. Exteriorly 

 the coral is marked by the. radiating costse, by lines of growth, which 

 usually are not very prominent nor closely set, and by much finer con- 

 centric striae, best seen by aid of the magnifier. Interiorly the polyp 

 is seen to be composed of a large number of lamell?e, among which 

 there is very little increase by intercalation, this usually taking place 

 through successive implantations at the various gaps. As might be 

 judged from the thinness of the coral, the lamellae are not very much 

 raised above the epithecal covering. Excepting near the center they 

 are little more than low ridges. At the center they seem to be slighlly 

 twisted together and to be slighdy depressed, forming a narrow shallow 

 cup ; our specimens do not show this part well. The number of the 

 lamellae of course varies with the breadth of the specimen. In the 

 first specimen mentioned there were about 130; the average is 12 or 

 13 along the margin in a distance of 10 mm. A cross section near 

 the center of the coral shows that at this point the lamellae are thin 

 and are crossed by vesicular tissue. The lamellre along the sides 

 are much indented in a manner similar to that characteristic of the 

 subdivision of this genus known as Heliophyllum. I however know of 

 no form of this genus which has any resemblance to this species. 

 Like the species last described it forms an interesting aberrant varation 

 of the genus. 



It will be noticed that .S". G. De Koninck quoted Ptycophyllum 

 patellatiim, Schlosheim from Dangelong. This is a species very 

 similar in form, may however be ever be superficially distinguished by 

 the fact that it has conspicuous elevations of long and short lamellae, 

 and that these begin to .be twisted already at a short distance from 

 the centre. 



CYATHOPHYLLUM BOLONIENSE, BlainvUk^ 



{Plate YAW, Fig. 15.) 



Corallum composed of numerous polygonal polyps. Polyps 

 typically five or six sided, but often with four, seven, or eight sides 



