June. i9-'i.] Crami'tox: Evolctiox of tiif. Axthropoda. 



99 



Fig. I 

 Fig. 2 

 Fig. 3 

 Fig. 4 

 Fig. 5 

 Fig. 6 

 Fig. 7 

 Fig. 8 



Pl.xtk VI. 



Mandible of Asclliis coiniiiu)iis (Isopod Crustacea). 

 Mandible of Diastylis sp. (Cumaccan Crustacea). 

 Mandible of Apseudes sfinosus (Tanaidacean Crustacea). 

 Mandible of Stegocephalus sp. (.^mphipod Crustacea). 

 Mandible of Machilis sp. (.^pterygotan Insecta). 

 Mandible of J'erbius costericola (Decapod Crustacea). 

 Mandible of Afysis stenolepis (Mysidacean Crustacea). 

 Swimming leg of young Limulus polypliemiis (Xiphosuran Mero- 



>tomata). 



Fig. ij. Mandibular appendage of opisthoparian trilobite, 

 becki. based on figure by Raymond. 



Fig. lo. Mandible of Nebalia bipcs (Leptostracan Crustacea). 



Triarthrus 



Pl.\te VII. 



Fig. II. Basal region of swimming leg of immature Liiiniliis polyphcmus 

 Xiphosuran Merostomata). 



Fig. 12. First gnathopod of Limulus polyphcmus (Xiphosuran Mero- 

 stomata;. 



Fig. 13. First thoracic limb of the branchiopodan crustacean, Liniiwdia 

 lenticularis, based on figure by Sars. 



Fig. 14. Gnathobase of third gnathopod of Limulus polyphcmus (Xii)ho- 

 suran Merostomata). 



Fig. 15. Swimming leg of eurypteridan merostome, Eusarcus, based on 

 fiKure by Clarke and Ruedemann. 



Fig. 16. Base of leg of Scorpio sp. fScorpionidan Arachnida). 



Fig. 17. "Coxa of fourth left endognathite seen from below " of eurypte- 

 ridan merostome, taken from figure by Clarke and Ruedemann. 



Fig. iS. Fourth thoracic limb of opisthoparian trilobite, Xeolenus, based 

 on figure by Walcott. 



Fig. 19. Sixth or seventh limb of Apus sp. (Branchiopodan Crustacea). 



Fig. 20. First limb of Apus sp. (Branchiopodan Crustacea). 



Fig. 21. First thoracic limb of syncaridan crustacean, Paranaspides la- 

 cuslris, from figure by Smith. 



Plate VIII. 



Fig. 22. Mandible of Apus productus (Branchiopodan Crustacea). 



Fig. 23. Mandible of Brauchippus rernalis (Branchiopodan Crustacea). 



Fig. 24. Mandible of Apus productus — same as Fig. 22, but in position 

 normally assumed when i>i silu. 



Fig. 25. Mandible of Conilera cylindracea (Isopodan Crustacea). 



Fig. 26. Mandible of Crmigon vulgaris (Decapodan Crustacea). 



Fig. 27. Mandible of male Gnathia maxillaris (Isopodan Crustacea). 



