GENERA OF FA VOSITID^E. 89 



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

 thickened lips 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 having 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 (PL 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- Ed wards 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 



