Anatomical Structure of certain of the Cetacea. 417 



EXPLANATION OF PLATE XV. 



Fig. 1. Cranium of the adult narwal seen from the upper surface. 



Fig. 2. The same cranium seen from below. These sketches were made with great 

 care. 



Fig. 3. The same cranium seen from behind. The want of symmetry is remark- 

 able. 



Fig. 4. The atlas, dentata, and third cervical vertebra of the same narwal. 

 Fig. 5. Cranium of a young narwal (supposed to be a foetus), seen from above. 



Fig. 6. One of the teeth withdrawn from the socket. The young narwal seems 

 uniformly to have two such, of nearly equal length ; one only comes to 

 perfection in the male ; neither in the female. 



Fig. 7. Inner surface of one of the compartments of the porpoise, in which there 

 prevails a peculiar structure, tubular or fibrous, and perhaps electrical. 



Fig. 8. Figure shewing the remarkable regularity of the tubes or fibres placed be- 

 tween two tunics of the stomach. 



