PLATE XXV. 



Illustrating paper by F. E. Lloyd on " The Mechanisms in certain boring 

 Lam ellibrauch Molluscs." Pp. 307-316. 



Fig. 1. Pholadidea penita; resting form. Eight side; the mantle cut 

 away along the dotted lines. The internal aspect of the mantle pore is 

 ehown at p, its front view at p^. 



Fig. 2. The same. Interior of left valve of resting form. 



Fig'. 3. The same. Right side of working form showing muscular foot. 

 The wall of the abdomen and the pulps are cut away so as to show the at- 

 tachment of foot muscles. 



aaa. accessory anterior adductor. 



aa. anterior adductor proper. 

 a. auricle. 



ab. abdomen, 

 ant. anterior. 



apx. antero-posterior axis, 

 as. accessory shell piece, 

 c. callum. 

 dvx. dorsi-ventral axis. 



f. foot. 



fl. posterior cuticular flap, 

 fm. foot muscles. 



g. gills. 



hx. hinge axis. 



p. mantle pore. 



pa. posterior adductor. 



pal. palps. 



pr. internal process. 



r. rectum. 



si. siphon. 



u. umbo. 



V. ventricle. 



va. ventral adductor. 



vpc. ventral point of contact ( =ventral tubercle). 



vt. ventral tubercle. 



