SOLEN. 243 



other ; there is, however, a sh'ght contraction of them near 

 the ligament, which is the narrowest portion of the shelL A 

 broad groove-hke excavation runs from the terminal beaks 

 to the opposite margin, stricturing as it were the anterior 

 extremity ; this latter is subtruncated, but the edge is con- 

 vex, and but little oblique ; the posterior termination, 

 which is, if anything, the broadest part of the valves, is 

 decidedly and almost rectangularly truncated. The in- 

 terior either partakes of the external colouring, or is of an 

 uniform whitish hue. The hinge is destitute of lateral 

 laminae, and consists of a single primary greatly com- 

 pressed prominent semicircular tooth in each valve, applied 

 to the corresponding surface of the other. 



The animal of Solen vagina is well known, having fre- 

 quently attracted the attention of malacologists for more 

 than a century. It differs considerably from that of either 

 of the preceding species; the differences, however, are only 

 of specific value. It is elongated and subcylindrical, the 

 mantle brownish-white, closed in front, and open anteriorly 

 for the i^assage of an oblong, compressed, yellowish-white 

 foot, which, when at rest, is subcylindrical, with an oblique 

 clavate extremity. The siphons are united to their extre- 

 mities, the tube so formed long as compared with that of al- 

 lied species, yellowish, and marked with concentric bands of 

 linear or moniliform brownish spots of unequal dimensions. 

 These circles seem to indicate so many stages of growth, 

 since they are evidently the remains of the brown markings 

 which surrounded the very short tentacles or cirrhi fring- 

 ing the siphonal orifices. The branchial orifice has an ob- 

 soletely fimbriated margin, and a circle of very short cirrhi 

 beyond it ; the margin of the anal aperture is plain, but 

 bordered beyond by a similar tentacular circle. The bran- 

 chiae are long, linear, and of an orange brown colour, and 



