No. 626] SHORTER ARTICLES AND DISCUSSION 



279 



It may be of significance that the only instances obtained of 

 fusions of the kind figured, occurred at a sandy beach, on the 

 south side of Bermuda, exposed to the beating of the ocean 

 surf. Individual A, when found, was attached to a rock, but 

 was half-covered by sand left by the tide. Chitons in such sit- 

 uations are frequently buried for a time beneath a foot or more 

 of sand, and under these circumstances the over-lapping edges 



of the shell-plates are kept tightly pressed together, thus pre- 

 venting sand-grains from abraiding the soft inter-tegmental 

 mantle. The posterior end of a Chiton tuberculatus is less 

 active in turning movements, in curling-up and in similar opera- 

 tions than is the anterior end, so that two valves, once stuck 

 together, might, at the posterior end, have a better chance of 

 remaining together. The incomplete union of the valves, visible 

 when seen from their inner side, suggests that the coalesced 

 plates started out independently. Whether or not this view be 

 valid, it would be of interest to determine if there is any gen- 

 eral tendency, in special localities, toward the establishment of 

 races of chiton possessing a reduced number of plates. 



"VV. J. Crozier 



Dyer Island, , 



