GENERA OE EAVOSITIDyE. 127 



some central foreign body. It is not that any particular stress 

 can be laid upon the mode of growth per se ; but so far as my 

 observations have gone as regards this species, this peculiar 

 habit is only found in specimens which have a special internal 

 structure ; and, under these circumstances, it becomes a charac- 

 ter of specific value. On the other hand, there occur along with 

 the preceding many specimens which form flattened or sub- 

 hemispherical expansions, having their under surface covered 

 by a wrinkled epitheca, attached to some foreign object by a 

 pedunculate base, having the calices confined to the upper sur- 

 face only, and not exhibiting any composition of the corallum 

 out of concentric layers. Specimens of this type in other re- 

 spects nearly resemble A. siLborbictdaris, Lam., and they might 

 be easily, and I believe sometimes have been, confounded with 

 the latter. So far as I have yet examined such specimens, 

 however, I find them to differ from the encrustingr and lami- 

 nated specimens which constitute the true A. sudor bicularis, 

 Lam., in various points of their internal structure, and especially 

 in the possession of numerous unusually strong spinose septa. 



The only points in the anatomy of A. stiborbictilai^is to which 

 I need draw attention are the condition of the septa and the 

 tabulae. According to Milne-Edwards and Haime, the outer 

 or under side of each of the calices 

 " bears interiorly a small elongated 

 ridge, which appears to represent a 

 septum, and is placed opposite to a 

 small notch" (Brit. Foss. Cor., p. 219). 

 Such septal ridges have been well 

 figured by Goldfuss, and I have re- 

 produced his drawing in order to show 

 their character (fig. 20). I am not able 

 to assert, however, that I have sue- ¥\g. 20.— CaWcts oi Alveolites sui>- 

 ceeded in detecting their presence by f"'?^' l-";-' ^'^fy ^"; 



o ir J Jaiged, showing the single septal 



an examination with a lens of any of "^ge. Devonian, Eifei. (After 



... 'IT Goldfuss.) 



the specimens in my possession, and I 



think that little specific value can be attached to a character 



