POLYPLACOPHORA. XIX 



Order POLYPLACIPHOKA (Polyplacophora Dall). 



Section I. Chitones regulares (EOCHITONIA Dall). 



Head and tail plates similarly articulated. 



A. LEPTOIDEA (Leptochitonidce Dall) 

 Insertion plates obsolete or, if present, unslit. 



(Extinct forms.') 



Helminthochiton Salter. Pterochiton Cpr. 



Gryphochiton Gray. / Loricites Cpr. 



Chonechiton Cpr. Probolwum Cpr. 



Priscochiton Billings. Cymatochiton Dall. 



(Recent forms.} 

 Leptochiton Gray. Hemiarthrum Cpr. 



Deshayesiella Cpr. Microplax Adams and Angas. 



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. 



Maugerella Cpr. Lepidoradsia Cpr. 



Spongiochiton Cpr. Callistochiton Cpr. 



**With girdlepores. 



Callistoplax Cpr. Ceratozona Dall. 



Angasia Cpr. Pallochiton Dall. 



Neivcombia Cpr. 



C. LOPHYROIDEA (LophyridcB Dall). 

 Insertion plates broad, pectinated, projecting backward. 

 Chiton Linne. Eudoxochiton Shuttleworth. 



Eadsia Gray. Craspedochiton Shuttleworth. 



Tonicia Gray. 

 Fannettia Dall. 



D. ACANTHOIDEA (Acanthopleuridce Dall). 



Insertion plates thrown forward. 

 ^Plates broad, pectinated (A. lophyroided). 

 Sclerochiton Cpr. 



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

 Acanthopleura Guilding. Corephium Gray. 



Lucilina Dall. Francisia Cpr. 



