MUSEUM OF COMPARATIVE ZOOLOGY. 267 



and the hooks on the terminal segment of the intervening three pairs 

 (from which the genus Polyonyx takes its name) are seen through the 

 outer, investing membrane. 

 Fig. 14. One of the abdominal appendages : «, the appendage to be disclosed at the 

 next moult. 



PLATE III. Porcellana (Polyonyx) macrocheles. 



Figs. 1-10. First stage of the crab. 



Fig. 2. One of the minute hairs of the front, highly magnified. 



Fig. 3. First antenna : a, basal (auditory) segment ; b, inner branch ; c, outer 

 branch. 



Fig. 4. Terminal segment of one of the ambulatory limbs. 



Fig. 5. Chela of the last thoracic appendage. 



Fig. 6. View from the front : a, eye ; b, first antenna ; c, second antenna ; d, 

 carapace ; e, basal segment of cheliped. 



Fig. 7. Abdomen. 



Fig. 8. Telson, after the first moult. 



Fig. 9. Third maxilliped : a, inner branch ; b, outer branch ; c, gill. 



Fig. 10. Appendage of fifth abdominal segment, right side from beneath : a, inner 

 branch ; b, outer branch. Similar appendages are found on the second, 

 third, and fourth abdominal segments. 



Figs. 11 - 21. Adult specimen from South Carolina. 



Fig. 12. First antenna of the right side, from below : a, basal (auditory) seg- 

 ment ; 6, inner branch ; c, outer branch. 



Fig. 13. Left mandible, seen from beneath : a, palpus. 



Fig. 14. First maxilla of the left side, seen from beneath : a, inner lobe ; b, outer 

 lobe ; c, palpus. 



Fig. 15. Second maxilla of the left side, seen from beneath : a, scaphognathite. 



Fig. 16. First maxilliped of the left side, seen from beneath. 



Fig. 17. Second maxilliped of the left side, seen from beneath : a, inner branch ; 

 b, outer branch. 



Fig. 18. Third maxilliped of the left side, seen from beneath : a, inner branch ; b, 

 outer branch. 



Fig. 19. Terminal segment of one of the ambulatory limbs. 



Fig. 20. Appendage of right side of third abdominal segment of female. A pair 

 of similar appendages exists on the third and fourth abdominal seg- 

 ments. 



Fig. 21. Appendage of second abdominal segment of the male : a, rudimentary 

 second branch. In this sex there is only one pair besides the swim- 

 merets of the sixth segment. 



PLATE IV. Pinnixa. 



Fig. 1. First stage of the zoea of Pinnixa chcetopterana, from Noank, Conn. 

 Fig. 2. Abdomen of the same : a, spine ; b, terminal piece of the telson. 

 Fig. 3. Second maxilliped of the same : a, inner branch ; b, outer branch. 



