358 MESSRS. H. A. NICHOLSON AND E, ETHERTDGE 



strom ('Ann. Nat. Hist.' ser. 4, vol. xviii. p. 12) that tlie well- 

 known coral described by Milne-Edwards and Haime under the 

 name of A. Fougtii is in reality only provided with oblique coral- 

 lites when young, and that in its adult state the tubes lose much 

 of their previous inclination, and the calices become simply irre- 

 gular in form. As A. Fougtii shows, in addition, the numerous 

 regularly arranged mural pores and the obscure septal striae of 

 Favosites, Lindstrdm has removed it from Alveolites to the latter 

 genus ; and the specimens which the Swedish palaeontologist has 

 kindly supplied to us would appear to fully warrant this step. 



In the second place, A. suborhicularis has the walls of the coral- 

 lites perforated by mural pores, which are admirably displayed in 

 polished sections. The pores are of large size, placed at irregular 

 but moderate intervals (from i to | a line or more) apart, and 

 arranged in single rows on the sides of the tubes. Though the 

 mural pores are few, irregular, and comparatively of large size, 

 and thus differ from the numerous, regularly placed pores of 

 Favosites, it is quite clear that this feature cannot possibly be 

 made one of generic value. Indeed, though excellently seen in 

 the present species, many of the forms with small tubes can hardly 

 be proved to possess these openings at all, save by some chance 

 specimen in some special state of preservation. The presence or 

 absence of mural pores is thus a feature upon which great classifi- 

 catory value cannot be set in practice, though theoretically the 

 point is one of high value and deserving of aU attention. In many 

 instances, however, even where the specimens are excellently pre- 

 served, it is impossible to determine whether mural pores exist or 

 not ; and this is particularly the case in Alveolites, where the tubes 

 are comparatively minute and the mural pores few and scattered. 

 In these cases one has hardly any thing to rely upon except the 

 chance that a transparent longitudinal section may lay bare the 

 wall of one of the tubes, and may thus bring to light the mural 

 pores. "Very often, however, longitudinal slices fail to reveal any 

 pores, even in forms which are with certainty known to possess 

 them ; so that the mere fact of their apparent absence can only be 

 allowed to count for very little. Moreover we have found that 

 numerous specimens of Favosites, in all other respects in a state 

 of the most admirable preservation, fail to exhibit the smallest 

 traces of mural pores, though these openings are both numerous 

 and close-set in this genus. It is therefore clear that the visibi- 

 lity of the mural pores depends greatly upon the condition of 



