56 PEOCEEDINGS OF THE MALACOLOGICAL SOCrETT. 



Two sides of this membrane are obviously attacbed to the branchial 

 lamella and branchial gland respectively, but the third side, that 

 extending from the branchial gland to the tip of the lamella parallel 

 to the mantle surface, is free. 



The skeleton with which this note is concerned consists of a series 

 of slender rods of cartilage (one to each gill lamella), standing out 

 from the branchial gland and stiffening the free edge of each sup- 

 porting membrane. Each rod tapers gradually from its base, which is 

 embedded in the covering of the branchial gland, till it reaches the 

 tip of the lamella; it is accompanied on its outer side by a slender 

 muscle. The cartilage of which the rods are composed agrees in 

 structure with that forming the major part of the skeleton, i.e. 

 branching cells embedded in an abundant hyaline matrix. 



