THE NAUTILUS. 



89 



small (3 mm. in diameter) it requires considerable adjustment to get 

 the shell properly balanced upon it, and it usually requires several 

 trials before the shell is finally placed in the proper balance. The 

 animal moves forward until the body is on a strain, then the shell is 

 hitched forward and over the operculum, on which it sometimes 

 catches at the first trial; more often this maneuver has to be repeated 

 several times before the shell is caught in the cup of the operculum. 

 When the balance is finally eflected the animal moves steadily away, 

 but with the rocking gait characteristic of the group. This species 

 is excessively timid, closing at the slightest jar, or when a shadow 

 falls upon it, and it then drops fr )m the surface on which it is crawl- 

 ing to the ground, and may lie still for several minutes before the 

 animal is again extended. On the other hand, it is vi'ry active and 

 quick in its movements, and liable to change its direction of motion 

 at any point. 



In this species the body is of a pale yellowish flesh color, with a 

 darker brownish pigmented mass down the back and running into 

 the rostrum and tentacles. The foot is the same color as the rest of 

 the body that is protruded from the shell. 



Comparing the three species upon which exact observations were 

 made, the results may be tabulated as follows: 



Comparison of motion of C. bronnii, T. feeundum and A. irrorala. 



Species. 



Colobostylus bronnii 

 Tudora feeundum . . 

 Adamsiella irrorata. 



i » 



70 millimeters. 

 50-60 " 

 50 



3 millimeters. 

 2 " 



1.25 " 



This method of progression is so different from that of most land 

 snails that other land operculates were examined for comparison. A 

 species of Helicina (//. neritella angulata C. B. A<1.) collected at Mon- 

 tego Bay, Jamaica, from which locality C. bronnii and A. irrorata 



