GENERA OF FA VOSITID.E. 89 



tures. The calices also (PI IV., figs. \a and 4 b) exhibit the 

 thickened Hps so characteristic of Pachypora, the proper wall 

 being still marked by a raised line which forms the crest of the 

 calicine margin. The characters of the calices differ to a con- 

 siderable extent in two different groups of examples. In one 

 of these groups — which at the same time comprises the smaller 

 forms, with the most regularly cylindrical branches — the calices 

 (PI. IV., figs. 4 and 4 a) are markedly circular or annular, open- 

 ing flush with the surface, and havinor a diameter for the most 

 part of about half a line. Mixed up with these larger calices 

 are smaller ones, which are also more or less circular, and vary 

 from a quarter to a third of a line in diameter. On the other 

 hand, in another great group of specimens — in which the cor- 

 allum is usually irregularly swollen, or even sublobate — the 

 calices (PI. IV., fig. 4 b) are more disproportioned in their 

 dimensions, the larger ones being from two-thirds to even 

 three-fourths of a line in diameter, while the small ones are 

 wedged in among the bigger openings, and are mostly poly- 

 gonal or angular. The large calices, also, are not always mark- 

 edly circular, but are often oval, and they have a decided ob- 

 liquity to the surface, which varies in amount in different speci- 

 mens. (I have never seen any example with an obliquity so 

 great as that figured by Milne-Edwards and Haime, Brit. 

 Foss. Cor., PI. LXI., fig. 4 a, where the front wall of each 

 corallite is free and exposed for a considerable distance ; but 

 I have seen an approach to this condition. Possibly this was 

 a weathered specimen.) Marked examples of these two condi- 

 tions may easily be selected, which are so different in appear- 

 ance that they might quite well be regarded as distinct species. 

 After an examination, however, of a large number of specimens, 

 I find the two groups to shade into one another so impercep- 

 tibly, that I cannot regard them as specifically separable. I 

 agree, therefore, with Milne-Edwards and Haime, who recog- 

 nised the two conditions of the species to which I have just 

 referred, and who regarded the smaller form, with the rounded 

 calices, as the type of the species ; while they figured the form 



