R. F. Tomes — Some Cretaceous Madreporaria. 543 



a large and spongy columella, that I had very properly suspected 

 both of being repi'esentatives of the same genus. Prof. Duncan's 

 species must therefore be removed into the genus Ceratotrochus, and 

 that genus must now be introduced into the English Coral fauna. The 

 specific resemblance between the two above named is so considerable 

 that some suspicion may well be entertained as to their distinctness, 

 but there are some particulars in which they differ. The English 

 form has the columella smaller, and the septa and mural costas are 

 much more uniform in size throughout. Moreover, the single row 

 of tubei'cles which ornaments the costee in both species are much 

 smaller in the English than in the French specimens. However, 

 they are very closely allied forms, and the one may very possibly 

 prove to be only a variety of the other. 



Trochocyathus Wiltshirei, Dune. Supp. Brit. Foss. Cor. pt. ii. 

 p. 34, pL xiv. figs. 10-12, 1870. 



Smiloirochus granulatus, Dune. loc. eit. p. 36, pi. xiv. fig. 17. 



The existence of a columella in the supposed Smilotrochus insignis, 

 and its consequent removal to another genus, naturally led to the 

 search for a columella in the allied species Smilotrochus granulatus. 

 The result was the discovery of that part surrounded by pali. A 

 subsequent investigation of the coralla of many species of varied 

 ages satisfied me that none of them are anything more than immature 

 examples of the species described by Prof. Duncan under the name 

 of Trochocyathus Wiltshirei. 



I may add that in the investigation of these small Madreporaria 

 from Folkestone, it is absolutely necessary that a good many examples 

 should be examined, and that some of them should be broken up, 

 otherwise their real affinities will be overlooked, as they appear to have 

 been by Prof. Duncan. 



Some of the immature examples of this species have so close a 

 resemblance to specimens of the foregoing species, which are of 

 corresponding size, that it is impossible to distinguish them, excepting 

 by ascertaining whether they have pali or not. 



Smilotrochus ? calcaratus, sp. nov. PL XIV. Figs. 1-5. 



The corallum is small, conical, and the inferior extremity is pro- 

 duced into a long oblique and slender, but flattened, spur, which, 

 when complete, has a ring of short rootlets at the end, by which it 

 may perhaps have been attached. 



The mural costee are distinct, rather large, equal in size, rounded, 

 and prominent according to their order. They are continued along 

 the spur, quite to the end. They have a single row of tubercles 

 along their central line, which are most distinct near the calice, more 

 especially in young specimens. In the larger, and therefore older 

 ones, the tubercles are nearly obsolete. 



The calice is circular, saucer-shaped, and the margin is rather thin. 

 The septa are a little exsert outwardly, near the margin of the calice, 

 but speedily curve inwards and downwards towards the fossula. 



