192 BRITISH FOSSIL CORALS. 



only in different specimens of the same species, but even in different parts of the same 

 specimen. The genus Axinura, established in 1843 by Count Castelnau for these 

 fasciculate Lithostrotions, or the division to which Professor Phillips had previously applied 

 Schweigger's generical name Lithodendron, and Professor M'Coy has more recently called 

 Siphonodendron, must consequently be abandoned. The genus Acrocyathus of M. 

 D'Orbigny is identical with M. Castelnau's genus Axinura, and therefore is our system of 

 classification united to Fleming's Lithosirotion. 



In most species of this group the multiplication of corallites evidently takes place by 

 gemmation, but the young individual which thus shoots from the side of the parent 

 corallites is sometimes produced very near the calicular margin ; and, in some of these 

 cases, rising up almost perpendicularly, makes the parent corallite deviate slightly from 

 its primitive direction, and may at first sight be mistaken for an instance of fissiparous 

 reproduction ; but the calice never showing signs of incipient division attendant on fissi- 

 parity, the appearance of a young corallite thus placed at the side of an adult one, and 

 compressing its calice, is not sufficient to authorise us to admit the existence of that mode 

 of multiplication. Mr. Lonsdale admits that some corals, otherwise resembling Lithostro- 

 tion, are in reality fissiparous, and it is on that ground that he has established the genera 

 Stylastraa and Diphyphyllum 1 which differ only from each other in being aggregate, and 

 consequently astreiform, or free laterally and fasciculate ; but the arguments which that 

 distinguished Palaeontologist makes use of in favour of this opinion, do not appear con- 

 clusive, and we therefore do not see sufficient reason for separating these genera from the 

 ordinary Lithostrotion. It is also on the presumed fissiparous mode of reproduction that 

 Professor M'Coy has separated from the latter (which, as has already been stated, he calls 

 Nemaphyllum,) the fossils that constitute his new genus Stylaxis? and differ from the 

 Stylastraa of Mr. Lonsdale, by the existence of a Columella, whereas that organ is not seen 

 in the latter; but its absence is probably only accidental, and due to the process of fossili- 

 sation, as is often evidently the case in common Lithostrotions. Till the alleged difference 

 in the mode of multiplication be more satisfactorily demonstrated, we therefore deem it 

 advisable not to separate Stylaxis from the old genus Lithosirotion, in which we also leave, 

 as above stated, Axinura, Stylastraa, and JDiphyphyllum. 



L. basaltiforme differs from the other astreiform Lithostrotions by its numerous and 

 thin septa. It is distinguished from L. Portloc/ci 5 and L. M'Coyanum 4, by the large size 

 of its calices. In L. ensifer 5 the columella is more prominent, the septa thicker, and the 

 walls very slightly developed. L. aranea 6 is closer allied to the above-described species, 

 but differs from it by its septa, which are not so closely set and more flexuous, and by its 

 columella being stouter. 



1 In Murchison, Verneuil, and Keyserling, Russia and Ural, vol. i, p. 621, 1845. 



2 Ann. of Nat. Hist., vol. iii, p. 119, 1849. 



3 See tab. xlii, fig. 1. 4 lb., fig. 2. 



6 See tab. xxxviii, fig. 2. 6 See tab. xxxix, fig. 1. 



