230 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Seh. 



As indicative of what careful and exhaustive collecting will 

 accomplish for such a group as the chitons, even in a re- 

 stricted locality, I may mention that Mr. Willett's first invoice 

 of specimens sent me from his 1914 collection included thir- 

 teen species. The number has since been increased to the 

 present total of twenty-four species and one subspecies, yet I 

 am certain that this figure is by no means complete for the 

 region involved, and perhaps not even exhaustive for the 

 collections as they stand. 



While the bulk of Mr. Willett's collecting was done at For- 

 rester Island, a small oceanic island at the extreme southern 

 end of the territorial jurisdiction, he also did some work at 

 the Waterfall Cannery on Prince of Wales Island, just inside 

 Cape Lookout on Dall Island, and at Sitka, all these last local- 

 ities being on the western or oceanic coasts of the island 

 chain, though protected from the open ocean itself, so that 

 the water is relatively calm. 



He reports that Tonicella lineata is everywhere by far the 

 most abundant shore chiton. This and Katharina (also abun- 

 dant) occur on rocks between tides, whereas Ischnochiton 

 mertensii (common), /. triiidiis (rare), Schizoplax, and Lep- 

 tochiton, characteristically occur on the under sides of rocks 

 "at pretty low tides ( — 1.0 foot)." Cyanoplax is another 

 characteristic shore form, being fond of crevices. In shallow 

 depths (15 to 25 fathoms), just beyond the kelp line, and 

 found mostly adhering to the inside of old mussel shells, oc- 

 curs an interesting association : Lcptochiton cancellatus, Ton- 

 icella lineata, juv. (common), T. ruber, T. siibmarmorea 

 (rather rare), Ischnochiton interstinctus (abundant), /. reti- 

 porosus, I. triMus (rare), /. mertensii (abundant), /. zvilletti 

 (common), Trachydermon fleet ens (rather rare), Mopalia 

 ciliata, M. imporcata, and M. sinuata. These occasionally 

 occur also on rocks hauled up in the dredge, but Mr. Willett 

 states that the shells are a favorite situs. Placiphorella rufa, 

 on the other hand, is found occasionally on shells, but gen- 

 erally on rocks. In deeper water (40 to 50 fathoms) Ischno- 

 chiton retiporosus was the only form commonly obtained. 



In the present paper two species, Isehnoehiton (Lepido- 

 zona) zvilletti and Placiphorella rnfa, are described as new. 



