I4O OILMAN A. DREW. 



EXPLANATION OF PLATE II. 



FIG. i. A specimen with the foot extended and the end of the foot swelled, the 

 instant previous to withdrawal. Drawn with the aid of an instantaneous photograph 

 made by Mr. J. G. Hubbard of a specimen held with the anterior end down, and 

 stimulated into activity. Natural size. 



FIG. 2. A specimen showing the usual position assumed in a dish of sea-water. 

 The siphons may be extended more than is shown in this figure. Drawn from ob- 

 servations. Natural size. 



FIG. 3. A specimen showing the position assumed just before leaping. Drawn 

 from observations. Natural size. 



FIG. 4. Ventral view of a specimen that has the foot extended to the position 

 shown in Fig. I. Drawn from observations. Natural size. 



FIG. 5. Direct view of the posterior end of an animal that has the siphons 

 extended. Drawn from observations. Natural size. 



FIG. 6. Direct view of the anterior end of a specimen that had withdrawn all but 

 the tip of the foot, showing the adjustment of the collar. Drawn from observations. 

 Natural size. 



FIG. 7. Anterior end of a specimen showing the position and shape of the foot at 

 the end of a burrowing movement. Drawn from observations. Natural size. 



FIG. 8. Diagrammatic cross section of an animal, taken just posterior to the ventral 

 opening in the mantle, to show how the mantle chamber is diminished by the contrac- 

 tion of the united mantle margins. Twice natural size. 



