Order POLYPLACIIMIOL'A (Polyplaoophora Dull;. 



Section I. Chitones regulares BoOHITON] \ I'ull;. 



Head and tail plates similarly artinilat* <!. 



A. LEPTOIDEA (Leptochitonidot Dall 

 Insertion plates obsolete or, if present, unslit. 



(Extinct forms.) 



Jlt'lininthochiton Salter. Pterochiton Cpr. 



Qryphochiton Gray. / Loricites Cpr. 



Choncchiton Cpr. Probolwum Cpr. 



Priscochiton Billings. Cymatochiton Dall. 



(Recent forms.) 

 Leptochiton Gray. Hemiarthrum Cpr. 



Deshayesiella Cpr. Microplax Adams and An gas. 



Hanleyia Gray. 



B. ISCHNOIDEA (Ischnochitonidse Dall). 

 Insertion plates sharp, smooth, fissured ; with eaves. 



*No pores on girdle. 

 Trachydermon Cpr. Ischnochiton Gray. 



Trachyradsia Cpr. Stenoplax Cpr. 



Callochiton Gray. Stenoradsia Cpr. 



Stereochiton Cpr. Ischnoplax Cpr. 



Tonicella Cpr. Heterozona Cpr. 



Schizoplax Dall. Ischnochiton s. s. Cpr. 



Leptoplax Cpr. Ischnoradsia Shuttleworth. 



Chcetopleura Shuttleworth. Lepidopleurus Cpr. 



Manger ella Cpr. Lepidoradsia Cpr. 



Spongiochiton Cpr. Callistochiton Cpr. 



**With girdlepores. 



Callistoplax Cpr. Ceratozona Dall. 



Angasia Cpr. Pallochiton Dall. 



Neivcombia Cpr. 



C. LOPHYROIDEA (Lophyridce Dall). 

 Insertion plates broad, pectinated, projecting backward. 

 Chiton Linne. Eudoxochiton Shuttleworth. 



Radsia Gray. Craspedochiton Shuttleworth. 



Tonicia Gray. 

 Fannettia Dall. 



D. ACANTHOIDEA (Acanthopleuridce Dall). 



Insertion plates thrown forward. 

 *Plates broad, pectinated (A lophyroidea). 

 Sclerochiton Cpr. 



**Plates sharp, grooved outside (A typica). 

 Acanthopleura Guilding. Cwphium < Jray. 



Lucilina Dall. Francisia Cpr. 



