PLATE VIII. 



Page. 

 PTERINOPECTEN SPIO 233 



Fig. 1. Loft valve, in which the surface has been largely removed, leaving the radiating 



costse and concentric lines in strong relief. Natural size, 

 la. Left valve, on which the concentric lines are faintly defined. Natural size. 



MACRODON TRUNCATUS 243 



Fig. 2. Left valve, enlarged to nearly three diameters. 



PLEUROPHORUS MEEKI 246 



Fig. 3. Cast of left valve. Natural size. 



STREBLOPTERIA SIMILIS 230 



Fig. 4, 4 6. Right valves. Natural size. 

 4 a, 4c. Left valves. Natural size. 

 4d. Finely striated left valve. See plate xix, fig. 7. 



PTYCHOPTERIA PROTOFORME 235 



Fig. 5. Left valve. Natural size. 



AVICULOPECTEN PlXTflENSIS 228 



Fig. C. Left valve. Natural size. 



CRENIPECTEN HALLAXUS 231 



Fig. 7. Cast of a large right valve. Natural size. 

 7 a. A small right valve. 

 76. A large left valve. Natural size. 



7c. Enlargement of the surface to show fine concentric striae crossing the radiating 

 plications. 



AVICULOPECTEN PEROCCIDENS 227 



Fig. 8. Left valve. Natural size. 



PTERIXOPECTEN HOOSACENSIS 232 



Fig. 9. Left valve. Natural size. 



