MOLLUSCA. 25 



state, high on the leaves of the Water Flag, having retired 

 from the moisture below. In the same manner, and from 

 causes equally obscure, some of the marine shelly mollusca, 

 as the Limpet, Periwinkle, and Trochus, may be observed 

 in a quiescent state on the rocks, above the reach of the 

 tide. A shower, however, in general excites the Succinea, 

 as well as the Limpets and Periwinkles, to motion, 



