192 BRITISH FOSSIL CORALS. 
only in different specimens of the same species, but even in different parts of the same 
specimen. The genus Aainura, established in 1843 by Count Castelnau for these 
fasciculate Lzthostrotions, 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 Avinura, and therefore is our system of 
classification united to Fleming’s Lithostrotion. 
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, im 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 
Stylastrea and Diphyphyllum* which differ only from each other in being aggregate, and 
consequently astreiform, or free laterally and fasciculate; but the arguments which that 
distinguished Palzontologist 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 Sfy/awis,” and differ from the 
Stylastrea of Mr. Lonsdale, by the existence of a Co/umedla, 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 Sty/azzs from the old genus Lithostrotion, in which we also leave, 
as above stated, dainura, Stylastrea, and Diphyphyllum. 
L. basaltiforme differs from the other astreiform Lithostrotions by its numerous and 
thin septa. It is distinguished from L. Portlochki*® and L. M‘Coyanum* by the large size 
of its calices. In Z. enszfer’ the columella is more prominent, the septa thicker, and the 
walls very slightly developed. Z. aranea® 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 beg stouter. 
‘ In Murchison, Verneuil, and Keyserling, Russia and Ural, vol. i, p. 621, 1845. 
2 Ann. of Nat. Hist., vol. iii, p. 119, 1849. 
® See tab. xlii, fig. 1. AV Tbe tioaes 
5 See tab. xxxviii, fig. 2. 6 See tab. xxxix, fig. 1. 
