MOLLUSCA. 71 



(Barb us vulgaris) of large size, and in a species of 

 Leuciscus. 



Insignificant as they may seem, the shells of 

 land and fresh-water mollusks, if collected dili- 

 gently by the traveller, and their localities cor- 

 rectly noticed, which may very easily and com- 

 pletely be done whilst he is on his journey, are 

 more likely to afford a clear notion of the geo- 

 graphical relations of its zoology than the few 

 specimens which time will permit him to prepare, 

 or chance throw in his way, of animals of higher 

 grade. Turning over a few stones, examining 

 the crevices in the bark of trees, the holes 

 and corners of rocks by the wayside, and the 

 bottoms of pools and streams, may often supply 

 him with numerous and valuable specimens ; and 

 if he takes due notes of locality, elevation, and 

 nature of soil, he may bring home in a very 

 small compass a treasure of valuable data for the 

 zoologist who is interested in the distribution of 

 animal life. We neglected no opportunity of 

 increasing our collection of the land and fresh- 

 water mollusca, and in all obtained between 

 sixty and seventy species ; a much smaller number 

 than might have been expected. But, as we shall 

 have again to observe when we come to write of 



