570 HAROLD HEATH, 



this situation, and several of these in the greatest abundance. The 

 eggs of one species, Ischnochiton magdaletiensis , were collected , and 

 their study forms the subject matter of the present paper, 



Ischnochiton magdalenensis, more often called Stenoradsia magda- 

 lenensis, was first described by Hinds ('44) from specimens obtained 

 from Magdalena Bay, Lower California. From this locality it extends 

 to Monterey Bay, where it is probably the most abundant species of 

 Chiton, and in gradually diminishing numbers we find it for a dis- 

 tance of 150 miles to the northward. Thus its range is from Magda- 

 lena Bay, Lower California, to Bolinas Bay, a few miles north of 

 San Francisco, California, or a total distance of about 1000 miles. 



All Chitons are probably vegetable feeders, and in Monterey Bay 

 and vicinity the majority are certainly nocturnal, withdrawing into 

 some shaded position upon the approach of day. Katharina, Toni- 

 cella ^ Nuttallina ^ occupying exposed situations on the rocks, and 

 concealing themselves but little, are apparently not highly sensitive 

 to light ; Mopalia and Cryptochiton will remain out on their feeding 

 grounds only when the day is foggy or dark ; the remainder of the 

 Chitons mentioned in the list conceal themselves under loose stones 

 or in crevices among the rocks, but none appear so highly sensitive 

 as I. magdalenensis. During the day this species may be found in 

 numbers of a score or more under such boulders as lie between tide 

 marks, half buried in the sand, and overgrown with various seaweeds. 

 During the night they come out to feed on this vegetation, sometimes 

 emerging completely, but more often just far enough to eat those 

 plants lying next to the sand. In these positions they may be found 

 in the early morning, but by sunrise all traces of them have dis- 

 appeared. 



The proboscis of the adults of this species appears highly sensi- 

 tive to light. Until they are about 4 cm in length it remains com- 

 pletely exposed as in other Chitons, but about this time a black or 

 dark green pigment is gradually deposited in the anterior eighth of 

 the foot, and in proportion as it deposits the foot is drawn more and 



Mopaliidae. 

 Mopalia muscosa Gtld,, M. muscosa lignosa Gtld., M. muscosa 

 hindsi 'Sow.' Rve., M. heathi Pils., M. ciliata Sow., Placiphorella 

 velata Cpk. 



Acanthochitidae. 

 Katharina tunicata Wood, Cryptochiton stelleri Midb. 



