APPENDIX. 



235 



From the above brief account, and from the accompanying illustra- 

 tions, it will be seen that Dittopora, Dyb., includes Monticuliporoids 

 of very much the same type as those placed by Dybowski under 

 Treviatopora, Hall, but distinguished by the comparatively unthick- 

 ened walls of the large coral- 

 lites, and the large size and 

 smaller amount of the angular 

 interstitial tubes. In the com- 

 plete isolation of the large cor- 

 allites by the interstitial tubes, 

 they resemble the species of 

 Fistidipora, M'Coy, but they 

 are distinguished by the pecu- 

 liar dimorphism of the corallum 

 above spoken of, and also by 

 the presence of the numerous 

 large - sized " spiniform coral- 

 lites." 



The known species of Ditto- 

 pora, Eichw., are from the Silurian rocks of Russia ; but I am not 

 acquainted with any form belonging to it, and I can give no more 

 detailed account of its characters than the above. 



Fig. 50. — A, Tangential section of Dittopora 

 clavaformis, Dyb., from the Silurian of Rus- 

 sia, enlarged, showing the circular large cor- 

 allites, the angular interstitial tubes, and the 

 large - sized spiniform corallites ; B, Vertical 

 section of the same, showing the large coral- 

 lites, with their very remote complete tabulas, 

 and the closely tabulate interstitial tubes. 

 (Copied from Dybowski.) 



