68 Mr. J. Thomson and Dr. H. A. Nicholson on the 



tending from the Upper Silm'ian (Wenlock Limestone) to the 

 top of tlie Lower Carboniferous. It appears to have attained 

 its maximum of development in the Devonian period. 



Genus Campophyllum. 



Campophyllum, Milne-Edwards and Haime, Brit. Foss. Cor., Intr. 

 p. Ixviii. (1850). 



Gen. char. Corallum simple, conical or cylindro-conical, 

 with an epitheca. Calice deep. Tabulae well developed, ex- 

 tending over a large central area, but not quite reaching the 

 inner surface of the theca. Outside the tabulate area is a zone 

 of vesicular tissue ; but this is mostly of inconsiderable thick- 

 ness. The septa are short, and do not nearly extend to the 

 centre, but leave the smooth upper surfaces of the tabulee ex- 

 posed over a large median space. At the circumference of 

 the visceral chamber the intersejDtal loculi are occupied by 

 delicate dissepiments (PL VI. figs. 3, 4, & 4 a) . 



As we have remarked before, the genus Gampophylliim may 

 be regarded as intermediate between the simple Cyathophylla 

 and Amplexus. The point in which the genus approaches 

 Gyathophyllum is found in the fact that the interseptal loculi 

 are filled up externally by fine dissepiments, which give rise 

 to a peripheral zone of vesicular tissue, in which the vesicles 

 are arranged in layers directed upwards and outwards. This 

 vesicular zone, however, is very rarely developed to any thing 

 like the extent which characterizes Gyathophyllum ; and it is 

 often filled up and almost unrecognizable. From the typical 

 Gyathophylla^ again, the genus is separated by the much less 

 highly developed condition of the septa, and the exposure of 

 the tabulae to view over a large central area. In this latter 

 feature, on the other hand, the genus closely approaches 

 Ani'plexus. 



The tabula? are comparatively remote and simple ; and the 

 area which they occupy is sometimes so great as to render the 

 distinction of examples from Amplexus a matter of difficulty. 

 The septa, though short, are always longer than in most of the 

 species of Amplexusj and they are united towards the circum- 

 ference by a moderate number of dissepiments. The dissepi- 

 mental vesicles are small and lenticular in shape. A septal 

 fossula is present, in some instances at any rate, and is formed 

 by a depression of the tabulae on one side of the corallum 

 (PI. VI. fig. 3). Short secondary septa are developed alter- 

 nately with the primary septa. 



In the absence of any certainty as to the precise forms in- 

 cluded by Prof. Dana in his genus Galop)hyllum, we are in 



