84 THE DISPERSAL OF SHELLS. 



the habit of procuring these animals for the market, 

 informed the observer that he had noticed the same 

 phenomenon in some other ponds in the neighbourhood. 

 Sometimes every one of the eight ambulatoiy legs 

 had a shell clinging to it, so that the animal appeared 

 as if wearing clogs. The shells in question are spoken 

 of as " Cyclas foniinalis" but as Mr. Heynemann, who 

 had the kindness to draw my attention to these 



KIG. 6. 



" Astacus fluviatilis & Cyclas fontinalis." After Girard, " Annales de la Socii^t^ 

 entomologique de France," (3), vii. (1859), pl> 4) fig* ''■• 



observations, points out, M. Girard describes and 

 figures a much larger shell (Fig. 6)} 



Professor Rossmassler ^ mentions that zebra mussels 

 {Dreissena polyrnorpha) have frequently been found 

 attached, by the byssus, to the tails of crayfishes. 



1 Professor Girard, 'Annales de la Societe entomologique de 

 France," (3), vii. (1859), 137-142. 

 ' As quoted in "Ann, and Mag. Nat. Hist.," (3), xviii. p. 494, 



