— 13 — 
Sect. 17. Katharina Gray. 
Valve cordiformes pallio profunde immers:, parte externa (Teg- 
mento) mediocri; lamina insertionis valde producta, valve antic#® 
9-lobata, postiee 4-lobata, mediarum bilobata; limbus corneus, lavis. 
Species eraminata. 
Chiton tunicatus Wood. California. 
Sect. 18. Cryptochiton Gray. 
Valve pallia omnino immers® et obteete (valve mediz utrinque 
bialate; lamina insertionis valv® antice 7-lobata, postic® late emargi- 
nate 3—4-lobata, mediarum obsolete bilobata); pallium spiculis fasci- 
eulatis subimmersis, ubique sparse obtectum. » 
Sectio mihi ignota, ex descriptione cl. Middendorf elucidata. 
Huc pertinet 
Chiton Stelleri Middendorf. 
Cujus synonyma secundum Middendorf, Chiton Sitkensis Reeve, Chiton 
Chlamys Reeve, et Chiton amiculatus Sowb. non Pallas. 
PLAXIPHORA. 
Pallium duplice serie pororum numero variabilium 
setas bifurcatas foventium, una ad marginem externam 
limbi, altera ad insertionem valvarum. 
Sect. 1. Euplaxiphora (Plaxiphora) Gray. 
Valve transvers®, externe; lamina insertionis valve antice circa 
9-lobata, postic® emarginatse integra, crassa, mediarum bilobata; lim- 
bus corneus levis, vel setosus, vel squamulis corneo-paleaceis plus 
minusve dense obsitus. 
Species examinale. 
Chiton biramosus Quoy. Nov. Zealand. 
»  petholatus Sowb. = 
Huc etiam ex speciminibus vel iconibus referendi, 
Chiton setiger King. Chili. 
„  setosus Sowb. Amer. centr. 
Obs. Sectionem secundam ex serie duplice pororum et valva postica 
eirca 10-lobata constituere videntur species sequentes mihi 
tantum ex speciminibus paueis not®: 
Chiton bipunctatus Sowb. Ins. Lobos. 
„  retusus Sowb. Amer, centr. 
