XXV111 POLYPLACOPHORA. 



Phylogenetic diagram of the genera of Chitonidce. 



H d 



o o 



^ .t3 



3 pd 



w o 



I 



'r3 



g 



Liolophurince 



CHITONIDCE 



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. 



