CORALS FROM THE MOUNTAIN LIMESTONE. 165 
Family SERIATOPORID &, (p. Ixii.) 
Genus RHABDOPORA, (p. lxiil.) 
RHABDOPORA MEGASTOMA. 
DeNDROPORA MEGASTOMA, M‘Coy, Ann. and Mag. of Nat. Hist., 2d Series, vol. ili, p. 129. 
1849 ; Brit. Paleoz. Foss., p. 79, pl. ui, fig. 11, 1851. 
RuHABDOPORA MEGASTOMA, Milne Edwards and Jules Haime, Brit. Foss. Corals, Introd., 
p. lxili, 1850; Pol. Foss. des Terr. Paleeoz., 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 coenenchyma granulated, 
or subechinulated, and obscurely striated.  Ca/ices 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 Seriatoporide 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 bemg 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 coenenchyma, 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 new 
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. 
