PLATE 26. 



Fig. 1. 470. 1. Pentameuus oblongus. ( Pag. 79.) 



la, b. A cast : views of the dorsal and ventral valves of a very large and gibbous specimen. 

 ] c. Cardinal view of the same, showing casts of the interlaminar spaces. . 

 i d. Profile view of the same, showing strong concentric ridges of growth. 



