GEOLOGY. 



67 



(Theea), &c, which attained a large size compared with the minute 

 shells of living members of this class. 



Gallery B. — The second of the wide Galleries has thirty-two 

 Table-cases and Wall-cases corresponding with Gallery A. In it are 

 placed the remaining groups of the Mollusca, viz., the Gasteropoda, 

 the Lamellibranchiata, and the Brachiopoda. It also contains the 

 Polyzoa, the Insecta and Crustacea, the Annelida and Echinodermata. 



Class 3. Gasteropoda (Snails, Whelks, &c). 



Class 4. Lamellibranchiata (Oysters, Cockles, &c). 



The fossil shells of the above groups occupy the whole of the West 

 or left side of this Gallery and a small portion of the East or right 

 side. Wall-cases 1-9 contain the Foreign Mollusca, and Table-cases 

 89-104 the British specimens of the same group. The Gasteropods, 

 or Univalves, are placed first in each case, and the Lamellibranchs, or 

 Bivalves, follow them. The whole series are subordinately arranged 

 in Stratigraphical series, commencing with the most recent deposits, 

 such as the Peat, Baised-Beaches, Glacial-deposits, and going back 

 in time to the Silurian and Cambrian periods. 



Attention is drawn to the fine series of Mollusca from the French, 

 Italian, and English Tertiary strata, particularly to M. Deshayes's 

 beautiful collection of shells from the Eocene strata of the Paris 

 Basin (Wall-cases Nos. 3 and 4), and the Miocene of Bordeaux 

 (Wall-cases Nos. 1, ( 2, and 3). To our own Eocene shells from High- 

 gate, Bracklesham, Barton, and the Isle of Wight (see Table-cases 

 Nos. 100, 101). This Molluscan fauna of the South-east of England 

 indicates the former existence of a much warmer climate in Britain 

 than we now experience. For such genera as Nautilus, Conus, 

 Valuta, Cyprcea, and Pleurotoma, then so abundant, do not now live 

 on our coasts, but must be sought for in subtropical seas. 



On the West wall, between Wall-cases 6 and 7, is placed a fine slab 

 of " Petworth Marble," entirely composed of the shells of a fresh- 

 water snail (Paludina). The elegant columns of the Temple 

 Church, Fleet Street, are made of this same marble from the Weald 

 of Sussex. 



In Wall-cases 5 and 6 are placed the curious shells called Hippu- 

 rites, allied to the existing Chamas. They probably lived clustered 

 in Coral-reefs like their modern representatives. They are seldom 

 met with in the Cretaceous rocks of this country, but the " Hippurite 

 limestone " is largely developed on the Continent, in France, Spain, 

 and Italy ; it also occurs in the East and West Indies. 



Among the Oolitic and Cretaceous Mollusca may be noticed the 

 shells of three genera, rarely obtained living in the seas of to-day, 

 namely, Pleuroiomaria (Table-case 93 and Wall-case 7), Phoktdomyd 

 and Trigonia (Table-cases 92-98). Only four recent specimens 

 of Pleuroiomaria have been obtained, one of which realized the 

 sum of £25. A single living species of Pholadomya is known from 



