30 



Anodonta cygnea var. Avonensis, the river Trent, 

 near Beeston. 



Anodonta cygnea var. Contorta, in the lake at High- 

 field House. 



Anodonta cygnea var. Veutricosa, in the lake at 

 Highfield House. 



With regard to the distribution of this shell through- 

 out England, Scotland, and Ireland, it seems every- 

 where to be abundant. It has also a range all over 

 Europe. Water fowl appear to feed upon it. 



As a fossil, we find it with Unio tumidus and Unio 

 pictornm, in the fresh-water tertiaries, at about the 

 period of the drift (Forbes). 



In the family Unionidce we are deficient of one mem- 

 ber, the Unio margaritiferus (of Linnaeus), which is an 

 inhabitant of rapid streams in mountainous districts. 



ApDENDA TO THE BlVALVE ShELLS. 



It will perhaps be interesting, as we proceed, to say 

 when each shell was first discovered, or added to our 

 British conchological catalogue. The following are 

 the various dates of the first descriptions of the bivalves, 

 and by whom described : — 



• Cyclas rivicola, described by Dr. Lister, in 1678. 



• Cyclas cornea, described by Dr. Lister, in 1678. 

 Cyclas caliculata, added by Montagu, in 1803, in his 



<' British Testacea." - , 



- Pisidium amnicum, described by Dr. Maton and the 



