PLATE 64. 
Page 
1-5. Platyceras plicatum. 334 
1. A young specimen in which no plications are developed. 
2. A more slender specimen in which the plications are strongly marked. 
3 & 4. A larger individual, in which the plications are but moderately developed. 
5. A large specimen which is compressed, the view showing a width greater than the natural 
width of the shell. 
6 & 10. Platyceras elongatum. 335 
6. A young specimen of this species. 
10. A large individual from which the extremity of the apex is broken, and the shell partially 
exfoliated from the lower part. 
7, 8, 9. Platyceras pyramidatum. 336 
7 & 8. Two views of the same specimen. 
9. View of a smaller specimen. 
