300 Mr. J. Thomson and Dr. H. A. Nicholson on the 



in Axophyllum is always simple, turbinate in form, with a 

 complete epitheca. The centre of the visceral chamber is 

 occupied bj a strong cylindrical columella, of comparatively 

 gigantic size, and formed of numerous vertical, spirally twisted 

 lamellae. Hence, on longitudinal section, the columella appears 

 as a cylindrical cellular mass of large size. The columella 

 pierces a central area, occupied by strong remote tabulse and 

 sun'ounded by an accessory wall. The space between the 

 inner mural investment and the true wall is occupied by dis- 

 sepiments, giving rise to an exterior zone of large vesicles. 

 The septa are well developed, and extend to the centre of the 

 visceral chamber. It will be seen from the above that the 

 structure of Koninckxyphyllum is entirely different from that of 

 Axophyllum^ as defined by Milne-Edwards and Haime (Pol. 

 Foss. des Terr. Pal. p. 455) and by De Koninck (An. Foss. 

 Nouv. Recherches, partie i. p. 23). Under these circumstances 

 it is unnecessary to add that the compound forms oiKonincJco- 

 phyllum cannot be confounded with Lonsdaleia^ the latter 

 having incomplete septa, which are not connected with the 

 external wall, and having a columella of a different structure. 

 So far as our present knowledge goes, the species oiKoninck- 

 ophyllum appear to be exclusively confined to the Lower 

 Carboniferous rocks. All our specimens are from Scotland 

 (Brockley, near Lesmahagow ; Charleston, Fifeshire ; and 

 Dunbar, Haddingtonshire). The compound forms are some- 

 times found in vast numbers, covering very extensive areas. 

 The description of the various species of this genus we reserve 

 for another communication. 



Genus Lonsdaleia. 

 Lonsdaleia, M'Coy, Ann. & Mag. Nat. Hist. ser. 2, vol. iii. p. 11. 



Oen. char. Corallum compound, fasciculate or astrjeiform, 

 increasing by calicular gemmation. Each corallite is provided 

 with a distinct wall ; and an inner mural investment is usually 

 developed. The centre of the visceral chamber is occupied 

 by a very large, somewhat cylindrical columella, formed of 

 twisted lamellae. A well-developed tabulate area of close-set 

 tabulse, surrounded by an exterior vesicular zone of large-sized 

 vesicles. The septa are present in the central area, most of 

 them falling short of the columella ; but they are not continued 

 through the peripheral vesicular zone to the outer wall. 



The corallum in Lonsdaleia is invariably compound, and 

 is either astraeiform or fasciculate. The young corallites are 

 produced by calicular gemmation, the new buds arising in the 

 outer vei^icular zone of the parent corallite, and the latter con- 



