240 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



is increased by the fact that the young do not always closely 

 resemble the adults, and the girdle characters, which seem to 

 be of the highest importance in separating the species, are 

 usually almost impossible to make out correctly in dried ma- 

 terial. The members of the sinuata-imporcata group are at 

 times particularly puzzling. Those having opportunities to 

 collect them should not fail to see that any bearded chitons they 

 may chance to find, however minute, are carefully fixed in the 

 expanded state and preserved in alcohol. No attempt should be 

 made to clean or dry them, lest valuable material lose much of 

 its significance. 



16. Mopalia ciliata wosnessenskii (Middendorff) 



Taken on shore at Forrester Island, at the Waterfall Can- 

 nery, Prince of Wales Island, and inside Cape Lookout, Dall 

 Island. 



The specimens are quite variable, some very elevated for this 

 subspecies, some depressed, and running through a whole 

 gamut of color forms. A few of the dried specimens from 

 Forrester Island are unusually long and narrow. 



17. Mopalia hindsii (Reeve) 



Seven specimens were taken at low tide on Forrester Island. 

 All are of exceptional size, one in Mr. Willett's collection 

 [S. S. B. 308] measuring in the dry condition as follows : 



Maximum length of animal 90 mm: 



Maximum width of animal 45.5 mm. 



Length of shell alone (not exact) 86 mm. 



Width of fourth valve inside girdle 36 mm. 



18. Mopalia lignosa (Gould) 



This is apparently a rare species in this region, as Mr. Wil- 

 lett took but one specimen at Forrester Island in 1914, none in 

 1915, and again one in 1916. Two were found near Cape 

 Lookout, Dall Island in 1915. All the specimens were taken on 

 shore. 



