16 



gryphsea virgula, &c. ; but at this end of the series it is impossible i. 

 obtain good specimens. At the shale works at Kimmeridge have bee 

 obtained fish, a dorsal spine, and a vast quantity of Saurian remains. 



ORGANIC REMAINS. 



The shells of the Purbeck beds, although abundant as to quantity, the 

 number of genera and species have been considered comparatively few. 



In the uppermost beds (A B and C) they are exclusively freshwater. 



At Peveral, good specimens of Unio maybe collected, both from theUnio 

 bed No. 8, and from the green deposits above. Paludina associated with 

 cyprides, beautifully weathered, may be obtained from the shales in the upper 

 bed of marl ; and in that below the marble, the thin band of light-coloured 

 marl contains a long small bivalve ; and the Paludina fluviorum occurs on 

 the surface of the Unio bed and also of the crocodile bed. No. 6. This last 

 is literally full of Unio, Paludina, bones, teeth, coprolites, and scales of 

 fish ; the marble is composed of the Paludina elongata, the upper part of 

 it contains Unio, teeth, and palates — next is the comminuted shell 

 limestone, composed of the cyrena. This and the following beds which 

 are classed under the heads D,E,F,G, contain brackish water, and marine 

 shells, amongst which may be mentioned three species of Melania, Corbulae, 

 and other bivalves. Pecten, cardium, avicula, &c. At No. 43 is a 

 band of paludina associated with cyclas ; this, when cleaved and weathered, 

 produces a slab frequently completely covered with these shells. 



The beds classed under the next head, H, contain freshwater shells, 

 with the exception of those which compose the Freestone quarry, namely, 

 from .58 to 62, which contain modiola, ostrea, and cardium, but having a 

 thin band with paludina, cyclas, &c. Many of the limestones in this 

 division are composed of cyclas ; good slabs of this shell may be obtained 

 from No 45. The Melania is frequent in these beds ; I first noticed it in a 

 thin hard blue shale immediately above the cinder. 



The upper cinder is composed of the Ostrea distorta. In the centre 

 band are two or three species of bivalves, and with them an echinoderm, 

 {Hemicidaris Purbeckensis), which was first noticed by Professor E. 

 Forbes in the autumn of 1849, and figured in the third decade of the 

 Memoirs of the Geological Survey. The lower cinder contains a Cardium 

 in abundance. Next below the cinder the beds (J and K, from 72 to 93), 

 contain purely freshwater shells, viz : — Valvata^ Paludina, Planorhisy 

 LymneuSj Physa, Cyclas, Unio, and a small univalve. Amongst these beds 

 Gyrogonites have been discovered at Ridgeway hill. These chert fossils 

 are more easily obtained from the blocks which lie upon the shore at the 

 west side of the bay ; the surface of some are covered with Unios. 

 Near Round Down, which is between Tilly Whim and Dancing Ledge, is 

 a spot at which a descent may be effected to the edge of the clitf, where 

 the lowermost chert bands are exposed, resting upon the Portland 

 oolite, where good specimens may be obtained, and likewise in the 

 ploughed fields where they are near to the cliff. The stone walls in 

 this neighbourhood, and especially those by the road-side between 

 Afflington Bam and Kingston church, will amply repay a close search. 



The beds from 94 to 128 (L) contain brackish water shells — Ldeda, 

 Avicula, and a small Cardium. 



Cyprides occur in many beds both above and below the Cinder, and 

 number four or five species. 



Remains of fish are abundant throughout the series, with the ex- 



