362 W. J. CROZIER 



length of the foot. In air, however, they are clearly alternate 

 ditaxic at the anterior end, corresponding to Parker's ('11) 

 analogy with the movements of a 'person in a sack walk.' In 

 Trochus, where the pedal waves are ditaxic but direct, Gosse ('65, 

 p. 8) long ago gave a somewhat accurate statement of this matter 

 and employed the same comparison: ''If your own two feet 

 were enclosed in one elastic stocking, your own progress would 

 appear very much like that of the Trochus," showing that he 

 had correctly appreciated the essential mechanical features of 

 this mode of progression. 



The foot of Conus agassizii is relatively large and bulky. In 

 full extension it measures 2 cm. x 4.5 cm., tapering somewhat 

 posteriori}^ but abruptly truncate at the anterior end. About 1 

 cm. from the anterior margin of the foot, in the midline, is lo- 



Fig. 1. Diagrammatic cross-section of the foot of Conus, showing the way in 

 which the foot is embedded in the mud. X f . 



cated the opening of the pedal gland: The ventral pedal sur- 

 face can be pressed out completely in contact with a smooth 

 surface, but usually this is not done. As collected, the shell is 

 commonly found in a horizontal position partially imbedded in 

 the mud, and it seems that the very distinct epipodial ridge has a 

 special functional significance for locomotion when the animal 

 is thus partly buried, although, as just stated, the distinction 

 between epipodium and foot proper can be obliterated. The con- 

 trol of the foot is in some respects distinctly bilateral. If one 

 side of the foot be touched lightly, that side as a whole is con- 

 tracted toward the shell aperture. This mode of response (seen 

 also in the fact that, if the shell be lightly pressed upon from 

 above, a distinct depression appears along the midline of the 

 foot, even though it may not be retracted) is undoubtedly con- 

 nected with the fact that the shell aperture is long and narrow, 



