159 



and overgrown with algae and other water plants. The 

 specimens procured of Uuio pictorum were alive, but 

 the whole of those obtained of Uuio tumidus were 

 deady and though in a good slate of preservation, the 

 epidermis was coated over with a black and shining in- 

 crustation, evidently owing to their being embedded in 

 a black boggy soil, and to the decomposition of the 

 water plants. This interesting discovery clearly illus- 

 trates that Unio tumidus cannot live in stagnant water; 

 it had flourished as long as the canal was a running 

 stream, but when it became unused, and the water stag- 

 nant, this species perished. Indeed, when I have en- 

 deavoured to keep Unio tumidus in confinement, it has 

 soon died; whilst Unio pictorum would, under similar 

 circumstances, live for a lengthened period. 



In the same canal were found the following species : 

 — Anodonta Cygnea, Paludiua vivipora, Limnaeus stag- 

 nalis, L. Auricularius, Bithinia tentaculata, and Physa 

 fontinalis. 



LOCALITIES OF MOLLUSCA. 



To illustrate which species will lire associated to- 

 gether, the following short extract from my "Note 

 Book" is appended. 



The dike which runs at the foot of Beeston, near 

 that village, contains a thick deposit of decomposed 

 animal and vegetable matter; the shells found in it are 

 Planorbis corneus, P. marginatus, P. vortex, Physa- 

 hypnorum, Valvata cristata, Cyclas caliculata, and 

 Pisidium pusillum; lower down, the stream becomes 

 clear, and the shells are very different : they are Physa 

 fontinalis, Limnoeus pereger, L, truncatulus, Succinea 

 putrls, var Pfifferi, Planorbis vortex, and Cyclas cornea. 



