1 64 THE GENUS MONTfCULIPORA. 



in contact, are seen dark, thick-walled, hollow tubes, which are 

 undoubtedly identical with the " spiniform corallites " of so 

 many of the Montiadiporce, though I am not acquainted 

 with the method in which they terminate at the surface. 



In tangential sections which intersect the corallum at a 

 deeper level (fig. 31, e), the large tubes are comparatively 

 larger, and are more strictly angular, while they are often 

 arranged in stellate groups or rosettes, consisting of four or 

 five tubes. The small intermediate corallites, being now 

 divided at a point nearer to their actual origin, appear to be 

 smaller in size as compared with the large tubes, and also, 

 upon the whole, less numerous. The thick-walled "spiniform 

 corallites " are also very marked in sections of this kind, one 

 being generally placed at the point at which two or three 

 of the laro-e corallites meet tocjether. • 



Vertical sections (fig. 31, f) show that the corallites, though 

 slightly bent at their actual point of origin, are essentially 

 everywhere perpendicular to the basal epithecal plate. They 

 are uniformly thin - walled throughout, and the larger coral- 

 lites are at once recognisable in consequence of the very 

 limited number of the tabulae which they possess, these struc- 

 tures being often wanting over considerable spaces, and being 

 always remote. When present, the tabulce are complete and 

 horizontal. In the small intermediate corallites the tabular 

 are likewise complete and horizontal, but they are now com- 

 paratively close-set, and crowded together. 



Yxovix M. pdropolitana, Pand., the present species is separ- 

 ated by the great development of the small interstitial corallites 

 as compared with the large tubes, the presence of spiniform 

 corallites, the comparative isolation of the large corallites, and 

 the remarkable difference in the tabulation of the two sets of 

 corallites. 



On the other hand, HI. Schuynii, Nich., is separated from 

 the present species by the greater proportionate development 

 of the large corallites, the much smaller size of the interstitial 

 corallites, and their aggregation at intervals into groups or 



