CORALS FROM THE MOUNTAIN LIMESTONE. 195 



5. Lithostrotion M'Coyantjm. Tab. XLII, figs. 2, 2a, 2d. 



Lithostrotion M'Coyanum, Milne Edwards and Jules Haime, Pol. Foss. des Terr. Palseoz., 



p. 444, 1851. 



This fossil much resembles L. Portlocki, but the corallites are smaller and much more 

 unequally developed; its inner walls are more distinct, and the septa less numerous, 

 (20 or 24,) somewhat thicker, and less unequal in size alternately ; they form a prominent 

 circle round the columella, which is also prominent. Diagonal of the large individuals 

 lj line, rarely 2 lines. 



Found at Oswestry and Matlock, Derbyshire. Specimens are in the collection of the 

 Museum of Practical Geology, of Mr. Bowerbank, and of the Paris Museum. 



6. Lithostrotion (?) concinnum. 



Diphyphyllum concinnum, Lonsdale, in Murch., Vern., Keys., Russ. and Ural, vol. i, p. 624, 



pi. a, fig. 4, 1845. 

 — latiseptatum, M'Coy, Ann. and Mag. of Nat. Hist., 2d ser., vol. iii, p. 8, 



1849. 

 Lithostrotion (?) concinnum, Milne Edwards and Jules Haime, Pol. Foss. des Terr. 



Palseoz., p. 446, 1851. 

 Diphyphyllum lateseptatum, M'Coy, Brit. Palseoz. Foss., p. 88, pi. iii, fig. 10, 1851. 



Corallites elongate, cylindrical, presenting slight circular growth swellings, and 

 surrounded with a thin epitheca. Inner walls rather distinct. Principal septa 32 in 

 number, very thin, and alternating with an equal number of small ones. Tabula well 

 developed, smooth towards the centre, the exterior zone occupied by oblique, slightly 

 vesicular dissepiments. Diameter from 3 to 5 lines. 



Found at Corwen and in the Oural Mountains. Specimens are in the collection of the 

 Cambridge Museum, and of M. de Verneuil. 



All the fossils of this species that we have examined were in a bad state of preservation, 



and the genus Diphyphyllum, established for them by Mr. Lonsdale, does not appear to us 



sufficiently characterised, for it differs from Lithostrotion only by the absence of the 



columella, and we have much reason to think that the non-existence of that organ is here 



merely accidental, and due to the process of fossilisation. The considerations which induced 



Mr. Lonsdale to form this new generic division were founded on the supposed fissiparous 



mode of multiplication of these corals ; but after close examination of their structure we 



are fully convinced that they are not in reality fissiparous, and that the appearance, which 



at first sight may be taken for a fissiparous division of the calice, is due to the rapid 



lateral coalescence of the young individual produced by gemmiparity and the parent 



corallite. 



26 



