12. 



paasions an.d so out of tlie cavity. The ricli nervous supply comes 

 as branches of the pallial nerves. 

 ■Anterior projections of the nantl_e,- 



The ant ero -ventral margins of the mantle may be pro- 

 truded a short distance beyond the margin of the shell, figiore 1, 

 and seems to aid in cleaning the foot when it is withdrawn from 

 the mud. These margins are destitute of tentacles b\xt are 



well siappl led with sense-papillae. 



Arising from each margin, opposite the extremity of the 

 anterior shell stripe, is an oblong projection, figure 1, a e. 

 This projection carries a row of sense-papillae, and is ciliated 

 on either side, figures 16 and 17. Branches of the anterior 

 pallial nerves can be traced very near, and they undoubtedly en- 

 ter, these projections. Enlarged pallial muscles, figure 17, 

 pm. act as their retractors. 



These organs are very sensitive to mechanical stimula- 

 tion, and probably serve as tactile organs, but their function 

 is not known. They are placed so near the edges of the retract- 

 ed foot that it is easy to think that they may serve some function 

 in connection with it, but no observations were made that support 

 this sT.irmise or that give a clue to any other fonction. 



