126 Mr. J. Thomson and Dr. H. A. Nicholson on the 



The genus Ei'idophyllum, Edw. & Haime, is, again, pre- 

 cisely similar to Diphyphyllum in all the essential points of 

 its internal structure, and differs only in the fact that the 

 corallites are united at intervals by abundant lateral outgrowths 

 of the epitheca. Occasionally, however, such epithecal out- 

 growths are sparingly developed in Diphypliyllum ; and we 

 are inclined to doubt if their absence or presence can be con- 

 sidered a ground of generic distinction. We do not think 

 that Dybowski has brought forward any sufficient reasons for 

 separating groups so closely allied, and placing them, as he 

 has done {op. jam cit. p. 81), in different families. 



The genus Dijylophyllum, Hall, was founded for the recep- 

 tion of some corals from the Niagara Limestone (Pal. N. Y. 

 vol. ii. p. 115), which in most respects agree with Diphy- 

 phyllumy but are stated to have the septa meeting in the centre 

 of the visceral chamber. They are also stated to possess an 

 inner mural investment smTOunding the central tabulate area. 

 This latter distinction, however, cannot be relied upon, since 

 an inner wall (though certainly wanting as a rule in Diphy- 

 phyllum) is stated by De Koninck to be present in D. con- 

 cinnumy Lonsd. Upon the whole, it seems probable that 

 Diplophyllum^ Hall, will prove on further examination to be 

 properly referable to Diphyphyllum. 



The geological range of the genus Diphyphyllum is a toler- 

 ably wide one. It appears to commence in the Upper Silu- 

 rian, being represented in the Guelph Limestones of Canada. 

 Several species are found in the Devonian rocks ; and the genus 

 is well represented in the Carboniferous. In the Carboniferous 

 rocks of Scotland the genus is rare, but it is represented by 

 the type species (D. concinnum, Lonsd.), as well as by another 

 form at present undetermined. 



Genus Lophophyllum. 



Lophophyllmn, Edwards & Haime, Pol. Foss. des Terr. Pal. p. 349. 

 and Brit. Foss. Cor. Intr. p. Ixvi. 



Gen. char. Corallum simple, conical, with a complete epi- 

 theca. Tabulae convex, in-egular, passing with more or less 

 interruption completely across the visceral chamber. A septal 

 fossette is present. A cristiform or clavate columella in the 

 centre of the uppermost tabula, joined by one extremity with 

 the single septum contained in the septal fossette, and some- 

 times connected by the other wdth the opposite primary septum. 

 Septa extending nearly, but not quite, to the centre of the 

 visceral chamber. 



So far as is known, all tlie species of Lophophyllum are 



