PLATE 32 C. 
1. 171. 18. Orthis sub.tttgata. (Pag. 129.) 
1 a. Ventral valve of a young specimen. X b. Profile view of the same. 1 c. Front view of the same. 
1 d. Dorsal valve of another specimen, with a deep sinus. 1 e. Front view of the same. 
1 f. Dorsal valve of an older specimen, showing the gibbous ventral valve projecting beyond the cardinal line. 
1 g. Front view of the same. 
I h. Dorsal valve of an old individual. 
1 i. Front view of the same, showing the deep sinus of the dorsal valve, and the corresponding elevation on 
the opposite valve. 
1 k, m. Cardinal views of young and old individuals. 1 n. View of the ventral valve. 
2. 170. 17. Orthis sintjata. (Pag- 128.) 
27, rn. Cardinal views of young and old specimens. 
2 n, o. Ventral valves of a young and old specimen. 
2 p. Interior of the dorsal valve, showing the form of the visceral impression, and the radii near the margin. 
2 q, r. The two lower figures show a slight difference in the character of the visceral impression. 
2 s. Interior of the ventral valve, showing the medial tooth, which is thicker and stronger than in the last 
species, and is connected with a strong medial ridge which is trifid below. 
