PLATE 26. 
Page 
'ig. 1 & 2. Spirifer perlamellosus. 201 
1 a - s. Illustrations of gradations of size and differences of form presented by this species. 
1 t. Enlargement of surface, showing the concentric lamella? [which 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 decomposition of the 
dental lamellae. 
2/,/. Cast of the ventral valve, and enlargement showing the papillose surface. 
2 g. Cardinal view of a cast of this species. 
