author's abstract or this paper is- 

 sued BY THE BIBLIOGRAPHIC SERVICE 



ON THE USE OF THE FOOT IN SOME MOLLUSKS^ 



W. J. CROZIER 



Bermuda Biological Station 



ONE FIGURE 



From time to time I have had the opportunity of observing 

 the method of locomotion in some mollusks which appear not to 

 have been studied previously from this standpoint; since these 

 observations add somewhat to our knowledge of the distribu- 

 tion and variety of pedal movements in chitons and in gastro- 

 pods, they may be briefly recorded. 



Ischnochiton purpurascens Ad., Acanthochites spiculosus 

 Reeve,- and an undetermined species of Tonicia were found to 

 agree with the two chitons whose locomotion has hitherto been 

 observed, namely, Acanthochites fascicularis (by Vies, '07) and 

 Chiton tuberculatus (by Parker, '11), since they all progress an- 

 teriorly by means of monotaxic retrograde pedal waves. They 

 add, therefore, to the conclusion (Parker, '11) that a certain 

 mode of pedal activity may be of general occurence throughout 

 single morphologic groups of creeping mollusks. Similarly, a 

 small species of Onchidiella I find to move by means of direct 

 monotaxic waves, like Onchidium (Vies, '07; Parker, '11); in 

 this Onchidiella the foo.t is quite small, 1.2 mm. x 3 mm., and 

 usually one, but sometimes two, waves are present on the foot 

 at one time. Three species of Crepidula which I have observed 



1 Contributions from the Bermuda Biological Station for Research, No. 100. 



^ This species or one of its so-called 'varieties.' Some of the 'varieties' re- 

 corded in the taxonomic literature of the chitons are nothing more than 'color 

 varieties' induced by the conditions of food supply, as I know from studies of Chiton 

 tuberculatus. The Acanthochites, now for the first time recorded from the Ber- 

 muda area, had brownish spinules, not greenish, as is recorded for some varieties 

 of A. spiculosus. 



359 



