PLATE 18. 
Strophodonta NACREA... 
Page 
. 104 
Fig. 1. 
1 a, b, c. Ventral valves of this species, showing varieties of form. 
1 d. A dorsal view of fig. 1 c. 
1 e. A profile of the same. 
1 /. A profile view of 1 a. 
1 g. Interior of the ventral valve. The open deltidium is due to accident. 
1 h' The interior of a dorsal valve. 
Fig. 2. Strophodonta ineqdistriata. 106 
2 a, b, c. Dorsal views of three individuals, showing the extremes of the ordinary forms. 
2 d, e,f. Ventral views of the preceding specimens. 
2 g. A profile of fig. 2 b- 
2 h. The interior of a dorsal valve. 
2 i. The interior of a ventral valve. 
2 k. The interior of a ventral valve enlarged to two diameters, showing the peculiar dental 
lamellae and the vascular impressions. 
Fig. 8 . Strophodonta textilis. 108 
3 a. A ventral valve of this species. 
3 b. A ventral valve which is more elongated than the usual form. 
3 c. The dorsal side of a large individual, showing the cardinal area of the ventral valve and a 
narrow callosity in the centre. 
3 d. The interior of a portion of an imperfect dorsal valve, showing the small muscular area and 
slender cardinal process. 
3 e. An enlargement of the surface, showing the character of striae, etc. 
4. A cast of a ventral valve which is apparently of the same species, much extended on the 
hinge line. 
