134 BLOOMER : ON THE BRITISH SPECIES OF THE GENUS SOLEN. 



is large, particularly as it approaches its distal end, where it is axe- 

 shaped and of considerable depth. The bases of the inner gills are 

 connected with each other, as in S. marijinafus, Pult. and Don. 



Musculature. 



The musculature of *S'. pelluridu>i differs from that of -6'. en>ii>i in the 

 following particulars, 



i. The Pallial Mii^de^i. — The muscles along the edges of the mantle 

 lobes are deeper than in IS. ensu, and anteriorly describe a semi circular 

 curve to the anterior end of the anterior adductor muscle (PI. x, fig. i, iT^.), 

 while posteriorly, where forming the proximal portion of the siphon, 

 they are much more developed (PI. x, fig. i, E.S.C and I.S.C). 



Th • posterior portion of the anterior adductor is deeper but the 

 depth gradually diminishes towards the anterior end, which curves 

 dorsally to the teeth of the shell (PL x, fig. i, A. A.). 



The posterior adductor is correspondingly smaller (PI. x, fig. i,P.A.). 

 ii. The Pedal Muscles — The foot increases in size towards its distal 

 end. In this part the muscles are frayed out, and form a large fibrous 

 network. The retractor pedis posterior muscles are longer, their ter- 

 minal parts being situated more posteriorly than in >S'. emis (PI. x, 

 fig. I, P.R.A.) 



In the retractor pedis anterior muscles, the posterior bifurcation 

 (Fig. I, P.R.A.) is short and thick, while the anterior one (Fig. i,P./^. J..') 

 is long and narrow extending over the greater portion of the anterior 

 adductor muscle. The fibres of the muscle cross the foot, as in 

 S. marymatus, and pass underneath instead of over the longitudinal 

 muscles, eventually becoming buried in the muscular integument. 



The Alimentary Canal. 



The oesophagus (PI. x, figs. 2 and 3. Oe.) is long and narrow, 

 passing in a posterior direction to the stomach, in consequence of which, 

 the latter is situated more posteriorly than in S. ensis. The divisions 

 of the stomach are very pronounced. The cardiac portion (Fig. 2, C. St.) 

 is a narrow, deep, pocket-shaped sac. The pyloric portion (Fig. 2, P. St.) 

 and the proximal portion of the caecum of the crystalline style (C.C.) 

 are very large, while the latter is of considerable length and extends 

 along the greater portion of the pedal cavity. The intestine {In.) 

 proceeds from the pyloric portion, close to the caecum of the crystalline 

 style, to within a short distance of its distal end, where it bends and 

 returns along the opposite side, traverses round the posterior dorsal 

 end of the stomach and folding upon itself, passes into the rectum (R.)- 

 If contrasted with the description of S. ensis and S. marginatm^ it will 



