K)SSIL FAUNA. 151 



PLATE LXVI. 

 Fossil Bivalve Shells. 



Fig. 1. A fossil Oyster {Ostrea Marshii, of Sowerby), from the Cornbrash of the Oolite, 

 "Wiltshire. 



Fig. 2. The fossil Cockscomb Oyster, (Ostrea carinata, of Lamarck,) from the Lower chalk, 

 Havre, France. 



Fig. 3. The elegant fossil shell here figured is a peculiar and most abundant species in the Lias 

 formation; specimens are not uncommon, in which every part of the shell is as 

 perfect as if just thrown up on the seashore. It belongs to the genus Gryphites 

 {Gryphea iucurva, of Sowerby,) the shells of which are nearly related to the oysters, but 

 are distinguished by the deep concave under-valve, and its curved beak, and the 

 almost flat upper shell. The testaceous substance is of a finer laminated structure 

 than in the Ostrea, and the hinge-ligament is inserted in an elongated curved groove.' 



Fig. 4. " Ostrea wl from folium.'" — Mr. Parkinson. This species appears to be the Ostrea 

 gregarea (?) of Sowerby, which occurs in the chlorite marl or firestone of the Lower 

 chalk in Sussex and Kent. 



Fig. 5. The fossil is the cast of an oyster-like bivalve, called Perna, {Perna quadrata, of 

 Sowerby,) which is easily recognisable, even in casts, by the line of distinct teeth 

 which compose the hinge. This species is abundant in the Portland limestone, 

 particularly in the quarries around Swindon, in Wiltshire; but from the close 

 adhesion of the outer surface of the shell to the surrounding stone, they can seldom 

 be extracted, the casts only being readily obtainable. In the Kimmeridge clay, which 

 lies above the Portland rock, the shells may be met with in great perfection. The 

 best locality is near Hartwell, in Buckinghamshire, where the clay is extensively dug 

 for the brick manufactures. 



Figs. 6, & 7. Two views of a small shell of the genus Crenatula, from Bedfordshire. 



Fig. 8. Portion of a very large species of Perna (Perna maxillata, of Sowerby), from tertiary 

 strata. Piedmont. The figure shows the inner surface of the shell with part of the 

 broad crenulated hinge. 



' Medals of Creation, vol. i. p. 387. 



