PLATE 26. 



Page 



Fig. 1 & 2. Spirifer perlamellosus. * 201 



1 a - s. Illustrations of gradations of size and differences of form presented by tliis species. 



1 t. Enlargement of surface, showing the concentric lamella? fwhicli are not strong enough in 



the figure] and the fine longitudinal striae. 



2 a, b. Interiors of ventral valves. 



2 c, d. Casts of the ventral and dorsal valves. 



2 e. Enlargement of a portion of 2 d, showing the cavities left by the decomjKjsition of the 



dental lamella;. 

 2/,/. Cast of the ventral valve, and enlargement showing tlie papillose surface. 

 2 g. Cardinal view of a cast of this si>ecies. 



