PLATE XIII. 



PlN^^A {ro. if i lined). 



Fios. 



]. y. liiiliiiiiihIii/,1, (I'Orl). LuwLT Greensaiid, Isle of Wight. Musouui of 

 Practical Geology, Xo. 12030. Veufcral part of right valve. (P. 90.) 



2, 3. ]'. sp. Gault, Folkcfctoiie. 2. Sedgwick Museum ; left valve. 3. Museum 

 of Practical Geology, Xo. 12041 ; portion of dorsal part of left valve, 

 X 0. (P. 99.) 



-J.-(i. r. decusmta, Goldf. Chalk. (P. 99.) 



4. Newtimber (Sussex). Bni,'htou Mii.seum. a, i-ii;ht valve; h, dorsal view of 



both valves ; c, dorsal jiart of right valve, x 3. 



5. Holaster planus mm;, \jj1»\vaui. Sedgwick Museum. Left valve. 



6. Tiiuiiughaui. Norwich Museum. Part of riLrht valve. 



