Structure of Heteropora neozelanica, Busk. 415 



desirable not only to select specimens which are externally 

 similar in shape and figure, but also to compare a series of 

 sections cut from precisely corresponding regions in both 

 groups of examples. In order to fulfil these conditions 1 have 

 chosen, in the first place, the Lower- Silurian Monticulipora 

 Jamesij Nich., which presents a close external resemblance to 

 Heteropora neozelanica, Busk ; and after briefly describing the 

 external and internal features of this, I shall give a short ac- 

 count of the characters of Monticulipora pulchella, E. & H., 

 in which we have a type of Monticulipora at least subgeneri- 

 cally distinct from M. Jamesi. I shall finally place toge- 

 ther in a summary form the characters in which Heteropora 

 and Monticulipora agree and those in which they differ. 



Monticulipora Jamesi, Nich. 



The corallum in this species of Monticulipora (fig. 3, A) is 

 dendroid, the branches varying from about i up to 



Fiar. 3. 



incl 



i in 



■~-im* 





A. Part of the corallum of Monticulipora Jamesi, Nich., of the natural 

 size. B. Part of the surface of the same, enlarged ; from the Cincin- 

 nati group of Ohio. C. Part of a typical specimen of Monticulipora ;>ul- 

 chella, Edw. & II., from the Wenlock Limestone of Dudley, of the natural 

 size. D. Part of the surface of the same, embracing one of the clusters 

 of large corallites, enlarged. 



diameter, dividing dichotomously, terminating in rounded free 

 ends, and sometimes becoming palmate by partial fusion. 



