GASTEROPODA. 241 



and bristles; at others, rough with numerous little 

 bony tubercles; it is also described as, in general, 

 fringed, so that when the animal attaches itself to 

 a rock or stone, it is altogether calculated by the 

 application of the prone part of its body, to produce 

 a vacuum. These animals are night feeders, remain- 

 ing stationary during the day ; they probably feed 

 on marine plants, the sea-wrack (Zostera), &c. 

 They slide along very slowly ; if accidentally re- 

 versed, they recover a prone position by the violent 

 motions of the ligament or zone that surrounds 

 them, and, if alarmed, they sometimes roll them- 

 selves like Wood-lice."* 



* Bridge water Treatise, vol. i. p. 271. 



THE WENTLETRAP (Scalaria Pretiosd). 



VOL. II. 



