MOLLUSCA (except CEPHALOPODA). 129 



Pliocene. The shells are primarily arranged under the 

 formations from which they come : the ]^orwich Crag and 

 the Eed Crag, both of Astian age ; the Coralline Crag, of 

 Plaisancian age ; the Lenham beds of Kent and the St. Erth 

 beds of Cornwall, both probably Plaisancian. No rocks of 

 Sicilian a^e occur in Britain. The Cracks are well known 

 for their abundant molluscan fauna, of which further 

 examples, mostly collected by the late Eobert Bell, are 

 exhibited in Cases A 2 (Lamellibranchia) and A 3 (Amphi- 

 neura, Gastropoda, Scaphopoda). The fauna is essentially 

 marine, but a few non-marine shells invite speculation as to 

 the cause of their occurrence. From the Coralline Crag of 

 Gomer, Suftblk, come some fine examples of the gastropod 

 Volicta Lamherti, one of them 9J inches (24 centimetres) 

 long. The Eed Crag furnishes Ncptunm antiqua wound in 

 a reverse direction to the usual one, Cyprina rustica, and 

 Pholas cylindrica. In the Norwich Crag again appears Acila 

 Cohholdiae, and Bittium rcticidatum is again found in the 

 St. Erth beds. 



Oligocene. Shells of this Epoch come from the Ham- 

 stead or Hempstead Beds of Eupelian age, the Bembridge 

 Limestone (Tongrian), and the Osborne and Headon Beds 

 (Priabonian). These formations were deposited in an estuary 

 where now are the Isle of Wight and the south of Hamp- 

 shire. One may notice \>d.Yi\Q\\Vdiv\Y Aiwphidromus [Buli7mos] 

 cllipticus wound in a reversed or left-handed coil, with many 

 species of the gastropod genera Vivipariis, Mclanici, Limnaea, 

 and PlanorUs cuom])]udus, and the lamellibranchs, Ostrea, 

 Corhicida, and Volsella \Modiolct]. The eggs of some large 

 gastropod, Buliimts or an ally, will be seen preserved in 

 Bembridge Limestone. A slab of Headon Limestone almost 

 entirely composed of the shells of a fresh-water snail, 

 Limnaea loiigiscata, is fixed on the w^all. 



Eocene. Here are the Bartonian shells of Barton, the 

 Lutetian of Bracklesham, and tlie Landenian shells from the 

 London Clay, Oldhaven Beds, A¥oolwich and Beading Beds, 

 and the Thanet Sands. Except for the Oldhaven and 

 Woolwich Beds, which contain both estuarine and marine 

 fossils, all these formations are purely marine. Many of 

 the specimens exhibited have been figured by G. A. Mantell, 

 James Sowerby, F. E. Edwards, and others. A large 

 specimen of Cardita 2)lcinicosta is marked so as to explain 

 the terms applied to the various parts of a lamellibranch 

 shell. Here also is the curious burrowing^ lamellibranch 



Gallery 

 VIII. 

 Table-case 

 2. 



Table-cases 

 2 & 3. 



Centre- 

 cases A2 

 A3. 



Table-case 

 3. 



Between 

 Wall cases. 

 2«&;3. 



Table-ease 

 4. 



Table-case 

 5. 



Table-case 

 4. 



