ERRATA. 



Page 11. for " Mytilus edulis," under cut, read " Unio." 



25. line 15. for " Tectibranchiata" read " Tetrabranchiata 

 133. for " Acmacacea," read " Acmaeacea." 

 176. for " Helix," under cut, read " Helix pomatia." 



