70 H. G. Carrnthers — A Revision of some Carboniferous Corals. 



in the upper portion of the coral the septa are impersistent, many of 

 them only reaching the centre of the coral as lines oa the surface of 

 the tahulte ; consequently there is a hare tabular area of considerable 

 size in the centre of some of the upper sections, while in the calyx 

 itself the bare tabular floor amounts to two -thirds the diameter of 

 the coral. 



A few fragments of a similar form have been found by Dr. Vaughan 

 at Cromhall, in association with more normal examples of the species, 

 including some of large size, but the evidence at present forthcoming 

 does not warrant the establishment of a distinct variety. 



A mutation of Z. honincki has been briefly described by Mr. Siblj'.' 

 The chief difference from the normal species appears to lie in the 

 large size of the coral and the more elongated minor septa. Similar 

 forms have been collected by Professor Garwood from Arnside (where 

 the normal species seems rare) together with a further mutation, 

 noticed by Dr. Vaughan, who has kindly supplied the following notes- 

 on the form^ : — 



" Z. koninclci, mut. Cg. — This mutation exhibits a marked convergence 

 with CyathophyUum 0, the dominant coral of the Cg beds. The form 

 is continuously conical and cornute, and the dimensions are large 

 compared with those of typical representatives of the species (the 

 average length is nearly 9 cm.). The septal plan is essentially that of 

 Z. konincki, but differs in the conspicuous elongation and distinctness 

 of the secondary [minor] septa. All the septa are attached to the 

 wall by short thickened bases, and the fossula has the elongated 

 parallel-sided section of that in most forms of Z. koniyicki. The 

 striking resemblance to CyathophyUum is caused by: (1) the 

 external zone radiated by primaries and secondaries " [major and minor 

 septa] ; " (2) the apparent development of vesicles in the internal area 

 (as seen in horizontal sections); (3) the type of fossula. The 

 differences are : ( 1 ) the apparent absence of vesicles in the external 

 area ; (2) the attachment of the septa to the wall by markedly 

 thickened bases." 



Remarks. 



MM. Milne-Edwards & Haime, in establishing the above species, 

 notice its similarity to the coral erroneously ascribed by them to 

 Michelin's Caninia cornucopice. In separating the two, they notice 

 that Z. konincki has (1) a circular instead of an oval calyx ; (2) thirty 

 instead of thirty-two septa, which are (3) thicker at their outer ends 

 and form a prominent lobe near the septal fossula ; (4) a fossula more 

 enlarged in the middle and not extending so far across the calyx, and 

 finally (5) ' altogether rudimentary ' minor septa. 



M. de Koninck's description (Nouvelles Recherches, etc., p. 99) 

 also agrees with theirs, but after showing that the French authors 

 were mistaken in their diagnosis of Caninia cornucopim he gives a new 

 name, Zaphrentis intermedia, to the coral they considered referable to 

 Michelin's species. 



' F. Sibly, " Carboniferous Limestone of the Mendip Area" : Q.J.G.S., vol. Ixii 

 (1906), p. 366. 



2 In these notes it should be understood that Z. komnchx is equivalent to Z. aff^ 

 cornucopia of Dr. Vaughan 's earlier papers. 



