ON THE GENUS ALYEOLITES ETC. 359 



fossilization, though it is very difficult to say why some specimens 

 should show them conspicuously whilst others, apparently in an 

 absolutely identical state of preservation and taken from the same 

 bed, show no traces of them. 



In the third place A. suhorMcularis possesses numerous com- 

 plete tabulae ; but these structures present nothing to distinguish 

 them from the tabulae of Favosites. 



Fourthly, the corallites of A. suhorMcularis are short, and are 

 superimposed on one another in successive concentric layers. 

 These characters, though sufficient to superficially distinguish spe- 

 cimens from examples of the more typical forms of Favosites, are 

 obviously of nothing more than specific value. Similar features 

 are found in some species of Favosites, while such forms of Alveo- 

 lites as A. septosa, Elem., have comparatively long corallites. 



Lastly, A. suborhicularis exhibits the curious feature that there 

 occurs on the outer lip of the calices a single elongated I'idge, which 

 is believed to represent a single primary septum. Our specimens 

 of this species, being wholly polished slices from the Devonian of 

 Devonshire, fail to show this character ; but it has been fully de- 

 scribed by Milne-Edwards and Haime, and it is excellently figured 

 by Groldfuss (Petref. Germ. Taf xxviii. fig. 1, Ji). That this tooth- 

 like ridge is, in the case of this species, truly a rudimentary septum 

 seems highly probable. It is apparently constant in position, and 

 in its development, and it appears to be present in all the calices 

 in well-preserved specimens. What may be its classificatory 

 value we shall discuss immediately, merely stating now that it is 

 evidently quite different in its nature from the so-called " septal 

 teeth " of such corals as A. septosa, Elem., and A. depressa, Mem. 



A. Labechei, Edw. & H., is in many respects closely allied to A. 

 suborhicularis, Lam. ; but Milne-Edwards and Haime state that it 

 has a septal ridge resembling that of the latter species, but only 

 " slightly developed," or " very indistinct." A. Grayi, Edw. & H., 

 is also closely related to the preceding, the septal ridge in the in- 

 terior of each corallite being " in general distinct, but not very 

 prominent." "We have not been able to examine this last-named 

 species fully ; but we have not succeeded in detecting the septal 

 ridge in such examples of A. Lalecliei as have come under our 

 notice (from the Upper Silurian of Dudley and of Sweden). 



A. compressa,^. & H., is another massive form allied to A. sub- 

 orhicularis. It is stated by Milue-Edwards and Haime to possess 

 three septal teeth, which do not differ in size. So far as our ob- 



