DE VEL OP ME NT. 6 1 



whereas the corallum in the discoid species of Monticulipora, 

 supposed to be developed out of the former, is usually and 

 normally/r£'«? ; but it is very difficult to explain this fact if there 

 be any developmental relationship between the two. Thirdly, 

 as regards matters of actual observation, I have never been 

 able to detect anything of the nature of a " Ceramop07'a stage " 

 in young Montiatliporce. This is a point which is most easily 

 observed in young examples of the discoidal species of Monti- 

 culipoj'a, such as M. petropolitana, and the various forms allied 

 to this ; and I can only say that the most minute examples of 

 these forms which have come under my notice differ in no 

 respect whatever, that I can detect, except size, as regards 

 their external and internal characters, from fully-grown speci- 

 mens. Fourthly, if it were the case that discoidal species of 

 Monticulipora, such as AI. petropolitana, Pand., grew out of 

 the thin parasitic crusts to which Hall applied the name of 

 Ceraviopora, we ought to be able to detect the primitive 

 " Ceramoporoid " portion of the colony at the base of thin 

 vertical sections of colonies of the former. I have, however, 

 examined a large number of such sections, and I have been 

 unable to detect any difference in the structure of the lowest 

 portion of the tubes, resting directly upon the basal epitheca, 

 as compared with that of the fully-grown portion of the coral- 

 lites. Dr Lindstrom states that the basal surface of a Monii- 

 aUipora, when its epitheca is very thin, " clearly shows that it 

 is a Ccramopora;''' but I am unable to concur in this statement. 

 If the specimen be undoubtedly one of MontiaUipora, then I 

 have never seen anything in its epithecal surface which could 

 be compared with the structure of Ceramopoi^a. All that can 

 be said, in my ©pinion, on this point is, that we meet in the 

 Palaeozoic rocks with specimens of the thin discoidal epithecse 

 of certain fossils (the LichcnalicB of Hall), which look like the 

 under surface of the epithecal plate of Monticulipora petro- 

 politana, Pand., but which might be really referable to quite 

 different forms (as many of them certainly are), and which 

 mostly cannot, without the preparation of thin sections, be 



