GENERA OF FAVOSITID&. 121 



be regarded as of generic importance at all ; so that the ulti- 

 mate existence of the genus will depend upon whether the type- 

 species, A. suborbicularis, Lam., can be shown to possess char- 

 acters which separate it generically from allied forms. In the 

 second place, the various definitions given by Milne-Edwards 

 and Haime yield, upon collation, the following characters as 

 essentially distinctive of the genus Alveolites as understood 

 by them : (i.) The corallites are furnished with lamellar walls, 

 and are not united by any ccenenchyma. (2.) The visceral 

 chamber is traversed by well - developed horizontal tabulae. 

 (3.) Mural pores, comparatively large and few in number, 

 are present. (4.) The corallites are oblique, shorter than in 

 Favosites, and terminated by oblique, semilunar, or subtrian- 

 gular calices. (5.) There exist in the interior of each corallite 

 three elongated teeth, which represent the primary septa, and 

 of which one is always larger than the others, and may be the 

 only one present. (6.) The corallites are arranged in the mas- 

 sive and incrusting forms in superimposed layers. 



Alveolites suborbicularis, Lam., the type -species, possesses 

 all the above-mentioned characters, and is therefore, to begin 

 with, clearly a member of the Favositidas proper. In order, 

 however, to establish the validity of the genus Alveolites, it is 

 further necessary to prove that A. suborbicularis is generically 

 separable from Favosites ; and there are only two of the above- 

 mentioned characters namely, the obliquity of the calices and 

 the presence of septal teeth which require special consideration 

 in this connection. Moreover, even if the generic distinctness 

 of A. suborbicularis and immediate allies be satisfactorily estab- 

 lished, there still remain various forms more or less resembling 

 this, which nevertheless differ considerably from it in minute 

 structure, and which must therefore be referred to different 

 groups. 



To the above remarks, taken from the paper already referred 

 to, was added a brief account of the principal types of structure 

 which are recognisable in the various forms which have been 

 at different times included under Alveolites by different palaeon- 



