214 INTRODUCTION TO CONCHOLOGY. 



against tliem^ and breakers scale the rocks, ay, siicli as might 

 wreck many a prond vessel, yet they heed them not. They 

 know that the winds and waves are messengers of good to 

 them ; and the moUusk who looks forth from his dweUing 

 when the waters have snbsided, sees aronnd him a plentiful 

 ])rovision for all his wants. 



Family TV. Fissueacea. 



•' Her place each wondrous creature keeps, 

 Amid unfathomable deeps." 



Shells pertaining to this family exhibit the channel by 

 which water is communicated to the branchial cavity, either 

 by an internal siphonal impression, by a marginal sinus, or 

 a complete perforation or fissure, and this in exact ac- 

 cordance with the habits and locaUties of each. 



The five genera are as follows : — Lottia, Sijjhonaria, Par- 

 moj^Jiorus, Eniargimda, and Fissiirella. 



The genus Lottia has been till lately associated with the 

 Patellce, as scarcely any difference is perceptible, except in 

 the arrangement of the breathing organs, which, instead of 

 being symmetrically disposed round the body, are situated 

 in a cavity at the back of the neck. 



