FAMILY " WITH HAED CHEEKS." 87 



of defensive plates along the sides of the tail, and by the 

 somewhat larger size of the teeth; in other respects it 

 differs but little, occurring in similar situations, and fre- 

 quently in the same shoal. The fin-rays are 



P. III.+10: P. 10: A. 1+9 : C. 19. 



THE SMOOTH-TAILED STICKLEBACK. 



This species is distinguished from those preceding it by 

 the side armour-plates, ten in number, extending no further 

 than the ends of the rays of the pectoral fin, the whole 

 length of the body behind these being smooth and soft, and 

 without scales. 



Fin-rays: D. III. + 10: P. 11: A. 1+8: C. 12. 



* leiurus, smooth-tailed, from leios, smooth, and oura, a tail, Gr. 



