EXPLANATION OF PLATE VIII. 



FiGUEE 36. — Squilla empusa Say, (p. 536;) lateral view of tlie free- swimming larva? 

 in one of its later stages, enlarged ten diameters. 

 37. — Zoea of tlie common crab, Cancer irroratus, (p. 530 ;) in the last stage just 

 before it changes to the megalops condition ; lateral view, enlarged 

 seventeen diameters. 

 38. — Megalops stage of the same, just after the change from the zoea condi- 

 tion ; dorsal view, enlarged thirteen diameters. 



(All tlie figures were drawn by J". H. Emerton.) 



