FLOOR.] 
FOSSILS. 
39 
J?zoc^mm, related to the recent Pearl-oyster ; Spondi/U; Scallops (Pec- 
ten), of peculiar form ; " Cockscomb " oysters, and species of Lima 
and Pleurotomaria. One peculiarity of the Chalk Fossils is, the con- 
stant absence of the interior pearly layers of the shells, which have 
been removed subsequent to their imbedding. In the Green-sand 
strata, Trigoni(B abound, and peculiar bivalves, of an extinct family (Hip- 
puritidcB), related to the recent Chama. Case 1, Eoom VI. 
6. JuEASsic, 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 Trigoni(B, 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 been moulded 
on TrigonicB and Ammonites. 
7. The Shells of the Teiasstc System in Case 4, Pioom V., con- 
sist of the original specimens figured and described by Dr. Klipstein, in 
his work 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 Koniuck, of Liege. 
10. Devonian System. (Case 5.) Devonshire and the Eifel. 
11. Silurian System. (Cases 5 and 6.) Presented by Sir Roderick 
Murchison. Bart., K.C.B. 
chambered shells {Cephalopoda). 
The Shells of the chambered univalves [Ce2)halopoda), velsited to the 
recent Nautilus and Cuttle-fish {Sepia), are placed in the Table Cases 
(7 to 12 and 14) of Room Y. 
In Case 10 are placed the curious fossils named Aptychi and Tri- 
gonellites, now known to be the operculum or covering to the mouth of 
the shell of the Ammonite. 
In Case 11 the fossil Nautili are displayed. Those from the London 
Clay of Highgate and Sheppey are specially worthy of notice. 
EOOM YI. 
Room Yl.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 soulliern 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 
