250 PROFESSOR NICHOLSON ON THE CORALS OF THE PALAZOZOIC PERIOD. 
Figure 1. 
Figure 2. 
Figure 3. 
Figure 
Figure 
Figure 6, 
Figure 7. 
Figure 8. 
Figure 9, 
Figure 10. 
EXPLANATION OF PLATE. 
A large example of Heliophyllum Halli, Edw. and H., producing a small tuft of rudimentary 
corallites by calicular gemmation at the termination of its growth. 
An example of the same, in which five calices have been produced in a vertical series hy 
simple calicular gemmation. 
Another example of the same, in which a single secondary corallite has been produced by 
simple calicular budding. 
4, Another example of the same, in which ordinary compound calicular gemmation has occurred. 
5. A simple individual of the same. 
Another example of the same, composed of two closely amalgamated corallites, which have 
either been produced by fission, or have grown accidentally side by side. 
An example of Heliophyllum subceespitosum, Nich., showing lateral gemmation. 
Another example of the same, showing the ordinary form of calicular gemmation. 
Cystiphyllum squamosum, Nich., showing a secondary corallite, developed at right angles to 
the original one by simple calicular gemmation. 
Cystiphyllum Ohioense, Nich., showing a secondary corallite developed in the axis of the 
original one by simple calicular gemmation. 
(All the specimens figured are from the Devonian formation, and all are drawn of the 
natural size.) 
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