HARD PARTS OF THE COMMON CRAB. 183 







8. First maxillipeds. 



9. Second maxillipeds. 



10. Third maxillipeds. 



11. First pereiopods, chelate. 



12. Second pereiopods. 



13. Third pereiopods. The oviducts open upon the 



sternal portion of this somite. 



14. Fourth pereiopods. 



15. Fifth pereiopods, swimming organs, with male re- 



productive orifices on their basal joints. 



16. First abdominal somite. First pleopods. 



17. Second Second pleopods. 



18. Third " " Third pleopods, absent 



in male. 



19. Fourth K Fourth pleopods, absent 



in male. 



20. Fifth " " Appendages absent. 



21. Sixth 



i. Draw the appendages, in their natural order. 



IV. On the ventral surface of the specimen from which 

 the appendages have been removed, notice that the car- 

 apace is reflected inwards along the sides, as far as the 

 bases of the legs, so that the opening by which water 

 passes under the carapace to the gills is a small, crescent- 

 shaped slit in front of the first pereiopod. Anterior to 

 the 'pereiopods, the lower surface of the carapace forms 

 the straight, longitudinal borders of the peristome. 



The anterior border of the peristome is formed by the 

 antennary sternum, or epistoma, \vhich carries a projecting 

 median spine, and is joined to the overhanging edge of the 

 carapace by the median rostral septum. 



V. The sternal plastron may now be removed, and 

 cleaned for examination. 



