PLATE XXX. 



Pkctkn {contiiitii'd). 



Figs. 



1,2. P. {CUuiiptoiiectes?) (jaultiau^, Woods. Gault. Woodwardian Museum. 

 1 (I, riglit valve, Folkestone, X 1\', 1 h, portion of the same near 

 the postero-dorsal margin X <3. 2, left valve. Black Ven, x 2. 

 (P. 163.) 



3—8. P. {Chlamy><) fissicosfa,'S:th. Woodwardian Museum. (P. 163.) 



3 — 6. Totteruhoe Stoue, Burwell. 



7. ,, ,, Ai-lesey. 



8. ,, „ Cherry Hiutou. 



3, right valve (type). 4, left valve (type). 5 a, riglit valve ; 5 &, part of the 

 same specimen x 2. 6 a, left valve x I5 ; 6 b, part of the same near the 

 antero-ventral border X 3 ; 6 c, another part near the middle of the valve 

 X 3. 7, right valve of a variety with few ribs. 8, left valve, crushed 

 near the umbo. 



9 — 12. P. {Chhniii/s) PicMsianvs, Math. Woodwardian Museum. (P. 165.) 



9. Cenomauiau, north of Beer Head, a, left valve ; b, postero-veutral part of the 



same X 2. 



10. Cenomanian, Wilmington, a, left vnlve ; b, part of the same near the centre x 2. 



11. Same locality. Eight valve. 



12. Top of Chloritic Marl, Melbury, North Dorset. Anterior part of right valve 



with the ornamentation well preserved x 2. 



