476 
THE GEOLOGIST, 
at all. la acquainting myself witli the organic remains of this rock, 
I found it most advantageous to work at the stone-heaps by the road- 
sides where it has been broken into small pieces, rather than at the 
quarry where some of it is not very frangible, and where it is all ill- 
exposed. This will both save labour and prevent disappointment. 
Very few genera of animals are represented in it, and scarcely any 
genus by more than a single species ; but the individuals are numerous, 
and so singularly persistent and distinctive in their forms that no 
better defined species could be desired. A small sea-urchin is very 
abundant and characteristic, but hitherto I only know it as an interior 
mould and cannot safely determine its genus. It is either an Acrosalenia 
or Pscudo-diadema ; but though I have collected as many as twenty 
or thirty specimens in a morning I am in almost total ignorance about 
the test. Once, too, and only once, I met with a trace of another and 
larger urcliin in the shape of a bit of an impression of (?) a Fedina or 
IIe7)iipedina. 
Thus there is a fair field at Hotham for any person interested in the 
JEcMnoidea ; and this last specimen may probably prove to be a new 
species. But some patience will be required for a successful hunt after 
these tantalizing little animals, whose shells, according to my experi- 
ence, are very difficult to be met with. 
Pinna, Modiola, and Pecten are the principal genera of shells ; and 
each has a single prevalent species. I shall not pretend to have ascer- 
tained these species. I neither know them myself nor can as yet 
obtain any reliable information respecting them. The whole zone is 
strange to me ; and while I am desirous to describe it as fully as I can, 
there is much in it that I mast leave for the present undecided. Any 
palaeontologist, being at Hotham, would have no trouble in collecting 
these shells ; and I should be glad to show such as still remain in my 
possession to any geologist visiting Cheltenham. 
In the miscellaneous drift-bed to the north of Hotham, which I 
discussed when speaking of Middle Lias, there occurs a rock so exactly 
resembling the " Ligniferous Marl " in appearance, that I had, till 
lately, no doubt of their identity, though I missed from it my fern- 
leaves, urchins, and mollusks. And when I found in it that typical-shell 
of the Upper Lias, Ammonites communis, and a faint impression of 
another Ammonite which seemed to be ^. Lythensis, I came fully to 
the conclusion, for the time, that my " Ligniferous Marl " was an 
