Prof. P. Martin Duncan — On Cretaceous Madreporaria. 53 



externally and concave towards the centre, and the fossa is large 

 and well marked, whilst the columella is fasciculate, broad, and 

 papillose at the surface in Cyclocyathus ; but in Micrabacia 

 the corallum is hemispherical and there is no large fossa in the 

 entirely convex calice, and the small columella has no papillae. There 

 are pali and no synapticulaa in Cyclocyathus, and there are no pali 

 and many synapticulaa in Micrabacia. 



The student of the Madreporaria who will turn to the figures of 

 the types of the two forms in the Pal. Soc. loc. cit. will have no 

 difficulty in recognizing their distinctness. Cyclocyathus is an 

 aporose coral, and Micrabacia is a true Fungid. Mr. de Wilde 

 drew M. Fittoni, nobis, from nature. 



Smilotrochus insignis, nobis (Pal. Soc. loc. cit. p. 37, pi. xiv. fig. 18, 

 1870). This is stated by Mr. Tomes to be a Ceratotrochus. The 

 morphology of Smilotrochus and Ceratotrochus was considered in my 

 "Revision of the Genera and Families of the Madreporaria" (Linn. 

 Soc. Journ. Zool. 1884), and it is noticed that Ceratotrochus is a 

 Smilotrochoid with a columella. The columella of this genus is 

 bundle-shaped and broad (fasciculate), 1 and processes arise from the 

 inner edges of the larger septa and ascend into it and add to its bulk. 

 The top of the columella is papillary and high up in the coral. The 

 specimen with a so-called columella I had not the advantage of 

 seeing, but there is a drawing of it in Mr. Tomes's paper (Geol. 

 Mag. 1885, PI. XIV. Fig. 6), and it is evidently a diagram. 

 What is considered to be the columella is not a fasciculate structui'e 

 gaining processes from the septa, nor is it a spongy columella, but a 

 mass of matrix which always fills up the lower parts of these corals. 

 The mass occupies the axis, and the rounded top is artificial. 

 Smilotrochus insignis, nobis, is not a Ceratotrochus, and one of the 

 reasons is that it has no columella. 



Smilotrochus granulatus, nob. (op. cit. p. 86, pi. xiv. fig. 17). This 

 is said by Mr. Tomes to be an immature TrochocyatJms Wiltshirei, 

 nobis. I should have been glad to have seen a specimen of the 

 interesting T. Wiltshirei, and still more to have seen the proofs that 

 a well-characterized Smilotrochus without columella and pali could 

 become a form with those essential characters in the growth of one- 

 tenth of an inch, and also increase from three to four cycles in the 

 same space. The height of the type T. Wiltshirei, nob., is three- 

 tenths of a inch, and that of the Smilotrochus is two-tenths of an inch. 

 The cyclical arrangement and the nature of the costas and of the 

 calice distinguish the two forms perfectly. There is no evidence that 

 one form could turn into another, and the species Smilotrochus granu- 

 latus, nobis, is not the same as T. Wiltshirei, nobis, for it has neither 

 columella nor pali. 



Podoseris mammiliformis, nobis, and P. elongata, nobis (Pal. Soc. 

 loc. cit. p. 25, pi. ix. figs. 2-17). These species are stated to be 

 species of Bhizangia, Ed. and H. To disprove this it would suffice 

 to draw attention to the above-mentioned figures of the types and to 

 the figures given of Bhizangia by Reuss (Denks. d. Wien. Akad. der 

 1 Not spongy as Mr. Tomes states. 



