PLATE XXXI. 



PiiOTOCA K I ij A {cull t innnl) . 

 Figs. 



1. P. (I iKjIiai, Woods. Lower Greeusand (Crackers), Atlit'i'fickl. Sedgwick 

 Museum, Cambridge. Eight valve. (P. 19k) 



2, 3. r. sphxroidea (Forbes). Lower Greensaud (/'r/«'(-l)e(l). (I'. 195.) 



2. Sandowu. British Muscuuj, No. L82-i7. a, k-il valve; h, dursul view ui' the 



same speciineu. x i. 



3. Atherfield. York Museum, k, left valve ; ^, posterior view of the same, x y. 



4. /'. sp. Upper Greensand, Haldon. Britisli Museum, No. L17<>ll. 

 Right valve. (P. 196.) 



o. P. sp. Speetoii Clay (zone of llclfinititcs intmilis), Speetoii. J\lr. Lamp- 

 lugli's Collection, a, I'ight valve X 2; b, dorsal view of both valves 

 X 2. (P. 197.) 



6. /'. liilliina (Sow.). Upper Greensand, lUackdowii. Sedgwick Museum. 

 a, left valve; /', posterior view of u ; c, part of the })osterior area 

 X 4. (P. 197.) 



