356 MESSRS. H. A. NICHOLSOJSr AND K. ETHERIJ3QE 



projections — one situated on the inside face of tlie outer lip of the 

 calice, the others opposite tlie preceding, upon the inner lip of the 

 corallite, and sometimes rudimentary. The calices are ohliq^ue, 

 subtriangular or subhemispherical. "Walls simple, well developed, 

 and pierced by a small number of pores. Tabulae complete and 

 horizontal.". ..." The elongated teeth or vertical projections 

 which we see in the interior of the visceral chambers of the coral- 

 lite^form the onost peculiar character of Alveolites, and recall the 

 three principal septa which characterize the genus Heterocoenia 

 amongst the Astrseidse. ... It is also worthy of note that one of 

 the septal projections is more developed than the other two, and 

 often it alone may exist. 



In briefly analyzing the above, it will be obvious, in the first 

 place, that Lamarck's definition of the genus Alveolites does not 

 contain a single character which, would at the present day be re- 

 garded as of generic importance at all ; so that the ultimate exist- 

 ence of the genus will depend upon whether the type species, A. 

 suiorbicularis, Lam., can be shown to possess characters 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 : — (1) The coral- 

 lites are furnished with lamellar walls, and are not united by any 

 ecenenchyma. (2) The visceral chamber is traversed by well- 

 developed horizontal tabulge. (3) Mural pores, comparatively 

 large and few in number, are present. (4) The corallites are ob- 

 lique, shorter than in Favosites, and terminated by oblique semi- 

 lunar or subtriangular ealices. (5) There exist in the interior of 

 eacb corallite three elongated teeth, wbicb represent the primary 

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

 be tbe only one present. (6) The corallites are arranged in the 

 massive 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 Tavositidee proper. In order, however, 

 to establish, the validity of the genus Alveolites, it is further ne- 

 cessary 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 con- 

 nexion. Moreover, even if tbe generic distinctness of A. suborbi- 



