PLATE XVIII. 



PAGE 



Fig. 1. Chonetes planumbona, M. and W 253 



1 a. Dorsal view. 



1 b. Ventral view. 



1 c. Surface markings, enlarged. 



1 d. Outline section, showing the arching of the valves. 



Pig. 2. Aviculopecten Oweni, M. and W 250 



2 n. View of right valve. 



2 b. Surface markings, maguified. 



2 c. Outline profile view of right valve. 



Fig 3. Aviculopecten oblongus, M. and W 258 



3 a. Left valve. 



3 h. Mould of same in matrix, without the hinge margin. 



Fig. 4. Aviculopecten amplus, M. and W 257 



4 a. Right valve, showing the deep sinus in the margin for the passage of 



the byssus. 



4 b. Ligament area. 



4 c. A large left valve, with surface somewhat worn. The dotted line 



shows, the position of muscular scar, as seen in another specimen. 



Fig. 5. Zeacrinus planobrachiatcs 240 



Side view of body and arms. 



Fig. 6 Pleurotomaria Shumardi, M. and W 260 



6 a. Side view showing the aperture. 



6 b. Opposite view. 



Fig. 7. Camarophoria subtrigona, M. and W 251 



7 a. View of ventral valve. 

 1 b. Profile view. 



7 r. Front view. 



/}. ^v^r^^f /«.wr. F »g- 8. Athtris planosulcata. Phillips? (sp.) 254 



8 a. Profile view of the two valves united. 

 8 b. Dorsal view of same specimen. 



8 c. Dorsal view of a larger specimen. 



8 d. Ventral view of last. 



