PLATE 31 
Iff-/, & 2 a - y. Khynchonella nucleolata. 
1 a, b, c. A young individual and one of medium size, having smaller plications than usual, 
and a larger number upon the mesial sinus. 
1 d, e,/. Larger individuals having stronger plications than the preceding, and a larger num¬ 
ber upon the mesial fold and sinus than those which follow 
2 a - e. Figures presenting the ordinary character of the smaller individuals of this species. 
2 f - t. Illustrations of the gradations in size, form, and proportions of this species. 
2 u, x, y. A cast of this species, showing the form of the muscular impression in the ventral 
valve, the median plate of the dorsal valve, and the alveolar cavities. 
3 a - d . Khynchonella abrupta. 
3 a , b. Dorsal and ventral views of a well-marked individual of this species. 
3 c, d. Front and cardinal views of another individual. 
