CORALS FROM THE MOUNTAIN LIMESTONE. 165 



Family SERIATOPORID^E, (p. lxiii.) 



Genus Rhabdopora, (p. lxiii.) 

 Rhabdopora megastoma. 



Dendropora megastoma, M'Coy, Ann. and Mag. of Nat. Hist., 2d Series, vol. iii, p. 129. 



1849; Brit. Palseoz. Foss., p. 79, pi. iii b, fig. 11, 1851. 

 Rhabdopora megastoma, Milne Edwards and Jules Haime, Brit. Foss. Corals, Introd., 



p. lxiii, 1850 ; Pol. Foss. des Terr. Palseoz., p. 305, 1851. 



Corallum subarborescent ; its branches coming off at an angle of about 70°; sub- 

 quadrangular, and differing but little in size. Surface of the ccenenchyma granulated, 

 or subechinulated, and obscurely striated. Calices arranged in a single row on each surface 

 of the branches, distant from each other, somewhat oval longitudinally, and having slightly 

 prominent edges. Twelve septal tubercles, somewhat unequal in size, and rather thick. 

 Diameter of the branches a little more than half a line ; long diameter of the calices about 

 the same. 



Found in the carboniferous limestone in Derbyshire, (Cambridge Museum.) 

 This coral is the only species belonging to the family of Seriatoporida that has as yet 

 been discovered in the carboniferous formation. It was referred, by Professor M'Coy, to 

 the genus Dendropora of M. Michelin, but we have considered it as constituting the type 

 of a peculiar generical division that differs from the former by the septa being more 

 developed and slightly exsert, by the tetragonal form of its branches, the mode of arrange- 

 ment of its calices, and the structure of the ccenenchyma, which is echinulate, slightly 

 striated, and not very compact, whereas in Dendropora it is quite compact, and its surface 

 completely smooth. Professor M'Coy, who appears to have taken only this last-mentioned 

 character into consideration, does not adopt a generical distinction between Dendropora 

 and Rhabdopora, because he argues that M. Michelin having overlooked the existence of 

 septa in Dendropora, may also not have noticed the granulations of the ccenenchyma. 

 But we must beg leave to remark that the observations of M. Michelin are quite foreign to 

 the motives which induced us to establish our genus Rhabdopora ; it is never from a 

 description, or a simple inspection of a drawing, that we feel authorised to propose neAv 

 divisions of that value, but it is from an attentive examination of the fossils themselves that 

 we have formed our opinion, and we are fully persuaded that if Professor M'Coy had been 

 enabled to study, as we have done, both the corals described by himself and that figured 

 by M. Michelin, he would have adopted the conclusions we have ourselves come to, and 

 have considered them as appertaining to two perfectly distinct genera. 



