CHAPTER IX. 



Siib-geims Prasopora, Nich. and Eth. jun., 1877. 

 (Ann. Nat. Hist., ser. 4, vol. xx. p. 388.) 



The name of P7'asopora was originally proposed by Mr R. 

 Etheridge, jun., and myself as a generic title for the recep- 

 tion of a small coral from the Craighead Limestone of Girvan. 

 I have, however, now discovered that two other Monticuli- 

 poroids (yJ/. Schvynii, Nich., and M. Newberryi, Nich.) have 

 essentially similar characters to P. Grayce, the original type of 

 Prasopora ; and I have therefore come to the conclusion that 

 it is best to regard Prasopora as simply a well-marked sub- 

 genus of Monticidipora. The admission of the above-men- 

 tioned species to Prasopora, also, necessitates some slight 

 chansfes in the diagnosis of the section, which will now include 

 forms with the following characters : Corallum concavo-convex 

 or discoid in form, sometimes free and with a concentrically 

 striated basal epitheca, more rarely attached by its base to 

 some foreign object. Corallites of two kinds ; the smaller ones 

 interspersed uniformly amongst the larger ones, or sometimes 

 partially disseminated through the colony, and partially aggre- 

 gated into clusters. Large corallites furnished with tabulae of a 

 twofold and peculiarly incomplete character, those of one series 

 forming a succession of marginal lenticular vesicles, enclos- 

 ing a central or lateral tubular space ; while the tabulse of the 

 second series are in the form of remote horizontal plates, cross- 

 ing the space included by the vesicular tabulae. The small 



