THE FISHES, MOLLUSOA, AND OTHER OBJECTS. 35 



pains which are required to prepare it for the 

 cabinet. The teeth in this species are not so 

 complex as in that just mentioned, and are usually 

 three lobed. For microscope purposes, the teeth 

 of another fresh- water univalve, Ancylusftuviatilit;, 

 are worth obtaining. This shell is commonly known 

 as the fresh-water limpet, and you may find it with 

 its base attached to the pebbles in any neighbouring 

 streamlet or brook, for it is fond of clear, running 



FiV. 22. 



A transverse row of the Lingual Ribbon of Succinea pittns. 

 Fig. 23. 



Portion of a transverse row of the Lingual Ribbon of Ancylus 

 fluviatihs. 



water. It well deserves its popular name, for it is 

 the counterpart of its marine relative, on a smaller 

 scale. There are about one hundred and twenty 

 transverse rows in the lingual dentition of this 

 mollusc. 



In the little runnels leading to our tarn, you may 

 find along the bottom, numbers of a small univalve 

 shell, not unlike the Paludina in general form. 

 This is the Bitliinia tentaculata, which forms such 

 an active and elegant object in the aquarium. 



D 2 



