PKOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 283 



"Chiton" Grat/aw MS Kouinck, 1857. Upper Siluriau. 



" ChUon" TVrif/htianus Kouiaek, ditto. 



" ChitotHlliin" Eaiicockianus Kirkby, Proc. Geol. Soc, 1859, pi. 16, figs. 1-13. Permian, 

 England. 



*' Chiton" cordatus Kirkby, ditto, figs. 24-29. 



'^Cltitotidluti" cUntortus Kirkby, ditto, figs. 28-30. 



" Chitonelliis" antiquus.Uow&e, Kirkby 1. c, figs. 14-23. Permian. 



" Chiton" cordifer Koninck, Descr. An. Foss. Terr. Carb. Belg., 1844, p. 324, pi. 22, fig. 

 5 a, 6 (teste Ryckholt). Carboniferous of Belgium. 



*' Chiton" corrmjalus Saudberger (pars), p. 238, jd. 26, figs. 22, 22 6, 22 c, 22(?, 1856. 

 Devonian and Lower Devonian of Vilmar and Ehrenbreitstein, 



'^Chiton" sagittalis Saudberger, 1. c., p. 239, pi. 26, figs. 23 a, b. Same locality? 



Suloochiton Grayi Ryckholt, Journal de Conchyl., lSii2, j). 259, pi. xii, f. 14. Carbonif- 

 erous of Vis^, Belgium. 



ABSTRACT OF ALL THE GENERA. 



Order POLYPLACIPHOEA. 



Section I. — Cliitones regulares. 



Head and tail plates similarly articulated. 



A. Leptoidea. 

 Insertion plates obsolete or, if present, unslit. 



{Extinct forms.) 



1. Helminth ochiion Salter. 



2. Gryphochiton Gray. 



a. Choriechiton Cpr. 



3. Priscochiton Billings. 



7. Leptochiton Gray. 



a. Deshai/esiella Cpr. 



8. Eanleyia Gray. 



4. Pterochiton Cpr. 



a. f Loricites Cpr. 



5. Proboheitm Cpr. 



6. Cymatochiton Dall. 



(Beeent forms.) 



9. Hemiarthrum Cpr. 

 10. Microplax Adams and Angas. 



B. ISCHNOIDEA. 



Insertion jjlates sharp, smooth, fissured ; with eaves. 



*No pores on girdle. 



11. 



12 



13. 



Trachydermon Cpr. 



a. Trachyradsia Cpr. 

 Calloehiton Gray. 



a. Sfereochiton Cpr. 

 ToniccUa Cpr. 



14. Schizoplax Dall. 



15. Li'ploplax Cpi". 



16. Chceioplenra Shuttleworth. 



a. Maugerella Cpr. 



17. Spongiochiion C]}t. 



18. IschnocMton Gray. 



a. Stenoplux Cpr. 

 T>. Stenoradsia Cpr. 



c. Ischnoplax Cpr. 



d. Heterosotia Cpr. 



e. Ischnochiton s. s. Cpr. 



/. Ischvoradsia Shuttleworth. 

 g. Lepidoplenrus Cpr. 

 h. Lepidoradsia Cpr. 



19. Callisiochiton Cjir. 



**With girdlepores. 



20. Callistoplax Cpr. 



21. Angasia Cpr. 



22. Newcomhia Cpr. 



23. 

 24. 



Ceratozona Dall. 

 Pallochiton Dall. 



