384 CARBONIFEROUS FOSSILS. 



longitudinal ribs. The oblique cup two inches broad, thick- 

 edged and deep, with the margin recurved, lined by about ninety 

 close and nearly equal lamellae (the intermediate ones being 

 as strong as the others) descending to the bottom of a deep 

 hollow a line broad, which surrounds the strong conical boss 

 in the centre. The latter is almost cylindrical, more than 

 half an inch broad and long, and much nearer to the concave 

 than to the convex side of the tube. A few only of the princi- 

 pal ribs rise upon it irregularly, and one of them forms a con- 

 siderably twisted ridge or crest. The boss is formed of close 

 vesicular tissue (apparently twisted when weathered), a more 

 open tissue occupying the spaces between the lamellae. 



At first sight one is inclined to separate this from Clisio- 

 phyllum, although in general form it is very like C. conisep- 

 tum or C. turbinatum of the mountain limestone. Milne 

 Edwards has particularly mentioned the ribs on the conical 

 axis of Clisiophyllum as straight, and in the English species 

 they are stout lamellae (inosculating a little) , and one of them 

 is generally elevated into a ridge or crest upon the boss. In 

 the Arctic fossil this crest is present, but carried up upon the 

 boss with a twist ; and the state of weathering of the boss it- 

 self in our specimen is so complete as nearly to obliterate the 

 straight lamellae, and show the complicated (and apparently 

 spiral) edges of its vesicular plates, so that it looks as if 

 it were a large simple species of Lonsdalia, as that genus is 

 defined by Milne Edwards (Strombodes of M f Coy). It is 

 however a genuine Clisiophyllum, and differs from all we 

 know by its very numerous equal lamellae, the secondary ones 

 reaching nearly all the way down the cup, and being as large 

 as the principal ones ; and further, by the great height and 

 prominence of the boss, which is narrow compared with the 

 breadth of the cup. The C. coniseptwn, Keyserling, has a 

 somewhat twisted arrangement of the lamellae, but a much 

 broader and less elevated boss. 



LOCALITY. Depot Point. 



