ON THE GENUS ALVEOLITES ETC. 357 



eularis aud its iuimediate allies be satisfactorily established, 

 there still remain various forms more or less resembling A. suh- 

 orMcularis, which differ considerably from it in minute structure, 

 and which must therefore be referred to different groups. In 

 what follows we shall briefly state the results of our examination 

 of a large number of such forms, which we may provisionally ar- 

 range in groups according to their affinities. We need only add 

 that our observations, when practicable, have been conducted by 

 means of transparent microscopic sections, as well as by the exa- 

 mination of the actual specimens themselves. 



Grroup A. Alveolites suborbicularis, Lamarch. 



The characteristic Devonian coral known under the above name 

 is thus described by Milne-Edwards and Haime (' Brit, Eoss, 

 Cor.' p. 219). 



" Corallum composite, forming irregular incrustated masses 

 which are in general fixed on ramose Favosites or on a Cyatliophyl- 

 lum, and are composed of superposed layers terminated by an 

 irregular or subgibbose surface. Galices very oblique, closely set 

 (but unequally so), elongated transversely, subtriangular, aud 

 turned towards the edge of the corallum. The outer or under 

 side of these calices bears interiorly a small elongated ridge which 

 appears to represent a septum, and is placed opposite to a small 

 notch. Transverse diameter of the calices about f of a line ; smali 

 diameter about half that length," 



As this is the type species of the genus, it will be advisable to 

 somewhat minutely examine its characters as set forth in the 

 above description, together with some others not mentioned 

 therein, with the view of determining, if possible, which of them 

 possess a more than merely specific value. 



In the first place, one of the most conspicuous external charac- 

 ters of Alveolites suborhicularis is that the corallites are oblique, 

 with the result that the calices are correspondingly oblique, one 

 lip being shorter than the other, and the aperture being more or 

 less elongated transversely, and subtriangular or semilunar in 

 ehape. Though this presents a superficially conspicuous feature 

 whereby to separate Alveolites from Favosites, it is quite evident 

 that this character is by no means one of generic value. Not 

 only is it possessed by forms otherwise different, but it is absent 

 in some corals which are usually placed in Alveolites (<?. g. in A. 

 septosa, Elem.). It has, moreover, been pointed out by Dr. Lind- 



