PLATE XIII Continued. 



Page. 

 PAL^OMANON ROEMERI 



Fig. 12. View showing the cup-shaped summit and general form. Owing to silicification, 

 the details of the structure are destroyed. 



ORTHJS IMPRESSA 115 



Fig. 13. Cast of ventral valve. Natural size. 



CHONETES MACROSTRIATA 126 



Fig. 14. Ventral view and outline of the convexity of an average size specimen. 



14 a. Same view of an unusually large specimen from which the striated outer surface 



has been removed, showing the inner punctate surface. 

 146. View of ventral valve of a small, strongly-marked specimen, to which a cardinal 



spine is attached; 14, 14 a, & are natural size. 



14 c. Enlargement of the striae of fig. 14, to show manner of bifurcation. See plate ii, 



fig. 13. 



CHONETES FILISTRIATA 127 



Fig. 15. Ventral view of average size specimen, showing surface striae and cardinal spines. 



15 . Enlargement of the area of the ventral valve, showing the shape of the foramen. 



PBODUCTUS HALLANUS 130 



Fig. 17, 17 a. Dorsal and ventral view of average size specimens. 



PRODUCTUS LACHRYMOSUS, var. LIMUS 132 



Figs. 18, 18 a. Lateral and front view of the ventral valve. 



PRODUCTUS SUBACULEATUS 128 



Figs. 19, 19 a. Ventral and cardinal views of a specimen from which the outer shell is par- 

 tially exfoliated. 



20,20o. Same view of the type of the species copied from plate ii, tome xi, Bull, Soc. 

 Geol. de France. The spine bases are stronger than in 19, 19 a, but in other speci- 

 mens they are much as in figs. 20, 20 a. See plate vii, fig. 2. 



