LAMELLIBKANCHIATA 



59 



The most beautiful forms occur in the chalk and greensand, 

 and resemble the recent scallop (Janira, Schum.) in the 



Fig. 14. 

 Secondary Bivalves. 



i. Gryphsea arcuata, Lam.; Lias, Ckarmoutk. 



2. Pecten (Neithea) quinquecostata, Sky. ; Chalk, Sussex. 



3. Pulvinites Adansoni, Defr. (internal mould) ; Corallian, Eoohelle. 



4. Gervillia anceps, Dh. ; L. Greensand, Isle of Wigbt. 



5. Inoceramus sulcatus, Park. ; Gaidt, Folkestone. 



6. Gucullrea (Macrodon) Hirsonensis, D'Arck. ; Great Oolite, Min- 



ckinkampton. 



7. Isoarca cordiformis, Sckloth. ; Corallian, Nattkeim. 



8. Myopkoria decussata, Miint. ; Trias, S. Cassian. 



inequality of their valves, but are further characterized by the 

 possession of articulating hinge-teeth like Spondylus. These 

 constitute the genus Neithea (fig. 14, 2). Plicatulce exist in the 

 trias and oolites, along with shells referred dubiously to Hinnites 

 and Spondylus. True Hinnites (a sub-genus of Pecte?i) are cha- 

 racteristic of the miocenc, Spondyli appear in the greensand and 

 chalk. Some of them (like the so-called " Plagiostoma spin- 

 os um") are unattached ; others resemble the recent deep-water 

 S. Gussonii, and have been called " Dianchone." The inner 

 layer, including the hinge of these shells, is seldom preserved. 

 Lima proboseidea first appears in the lower oolite, and reappears 

 in the great oolite, and in the Kelloway rock. Lima duplicata, 



