POLYPLACOPHORA. 



Pliylogenetic diagram of the genera of Chitonidce. 



I I 

 w 6 



S o 



3 M * 



2 '" 9 



I J -a 



^ PH O 



.tn o ri 



Liolophurince 



CHITONID^E 



ANALYTICAL KEY TO GENERA OF POLYPLACOPHORA. 



a. Valves lacking insertion plates, or if present they are unslit 

 (Lepidop leuridce) . 



b. Valves entirely exposed, not immersed, 

 c. Insertion plates completely absent, 



LEPIDOPLEURUS, p. 2. 



cc. Head valve having an insertion plate, grooved 

 outside but unslit ; valves ii-viii without plates, 

 girdle spinulose HANLEYA, p. 17. 



ccc. Head and tail valves only having unslit insertion 

 plates; girdle thick, sparsely downy, with sut- 

 ural pores HEMIARTHRUM, p. 19. 



