PLATE 4-2. 



Pogs 



Fig. 1 a - r. Atrypa reticularis. 253 



1 a, b, c, d. Ventral and profile views of young specimens. 

 1 e. Dorsal view of the ordinary form of large individuals. 



1/, g, h. Dorsal, front and profile views of a specimen from the Upper Pentamerus limestone. 

 1 {, *, I. Dorsal, ventral and profile views of an elongate or ovoid form of this species. 

 1 m. Interior of the dorsal valve. 



1 «. Interior of the ventral valve, showing the teeth, muscular area, and tlie va.scular im- 

 pressions. 

 1 0. The ventral valve of a smaller individual. 



1 p. A specimen with the dorsal valve partially broken away, showing the internal spires, 

 which, by mistake of the lithographer, are represented as one. 



] r. Front view showing the arrangement of the spires. 



