32 
NOKTH GALLERY. 
[upper 
6. Jurassic, or Oolitic Shells. (Cases 2 and 3, Room V.) The 
shells of the Portland stone, Bath stone, and other Oolitic rocks, and of 
the Lias, include numerous species of Trigonim, the internal casts of 
which are often found whilst the shells have been dissolved and removed 
from the rock ; they are called *' horse-heads " by the quarry-men, and 
are sometimes silicified, and contain traces of the shell-fish itself. 
Amongst the Oolitic oysters, are some whose shells have heen moulded 
on Trigonim sand Ammonites. 
7. The Shells of the Triassic System in Case 4, Room V., con- 
sist of the original specimens figured and described by Dr. Klipstein, in 
his wo-rk on the fossils of the salt-marls and Alpine limestone of 
Austria. 
PALEOZOIC shells. 
8. Magnesian Limestone (Permian), of Northumberland and 
Durham. (Case 4.) 
9. Carboniferous Limestone, and Coal-measures of Britain and 
Belgium. (Cases 4 and 5.) Chiefly from the collection of Professor 
De Koninck, of Liege. 
10. Devonian System. (Case 5.) Devonshire and the Eifel. 
11. Silurian System. (Cases 5 and 6.) Presented by Sir Roderick 
Murchison. 
chambered shells (Cephalopoda). 
The Shells of the chambered univalves [Cephalopoda), related to 
the recent Nautilus and Cuttle-fish [Sepia], are placed in Table Cases 
(7-14), of Room V., and are grouped in geological order. 
Those of the Chalk, Gault, and Green-sand, include the collection 
of M. Astier from the south of France ; and the oolitic series has 
recently been enriched by the collection of M. Tesson, of Caen. 
ROOM YL 
Room VI. is occupied chiefly by the osseous remains of the Edentata 
(quadrupeds without front teeth) and large Pachydermata (thick- 
skinned herbivorous quadrupeds), such as the Elephants and Masto- 
dons. Of the Edentate order of quadrupeds, the most striking example 
is presented by the skeleton of the Megatherium. The remains of 
this animal have been met with in the southern parts of South America, 
and more especially in the region of Buenos Ayres. A slight acquaint- 
ance with the bony framework of animals may enable the visitor to 
appreciate the enormous muscular power which this animal must have 
possessed ; the huge Mastodon near it must have been a comparatively 
feeble animal. The strength of the Megatherium is indicated by the 
form of the bones, and especially their tubercles and ridges, to which 
the muscles were attached. In the fore parts of the body the frame- 
work is comparatively slender ; the contrary is the case with the hind 
quarters, where enormous strength and weight are combined, indicating 
that the animal habitually rested on its haunches and powerful tail. 
