BLOOMER : ON THE BRITISH SPECIES OF THE GENUS SOLEN. 43 



The folding and exact position of the folds vary somewhat in 

 different specimens, but this is probably due to the extent of the 

 contraction or distension of the proximal part of the foot. 



When the intestine leaves the stomach, the wall on the one side is 

 invaginated, and forms the typhlosole, which extends along the 

 convoluted part of the intestine (PI. ii, fig. 2, C.In.) near to where it 

 passes the distal end of the caecum containing the crystalline style. 



The typhlosole commences with a slight invagination of the wall 

 of the intestine, this gradually increases in size and flattens out (PL iii, 

 fig. 8, Tij.); at the same time, its walls become folded, and the width 

 across the base is diminished. Towards its termination, it decreases 

 in size and ends in the folded walls of the intestine. 



The typhlosole is lined with ciliated epithelium, and the inside of 

 it is filled with connective tissue. A transverse section of S. siliqiia 

 (PI. iii, fig. 9, Ty.) across one of the first convolutions show the 

 typhlosole of the one fold to be joined by connective tissue to the 

 typhlosole of the opposite fold, without any divisional wall. 



The tricuspid body, or the fleche tricuspide, in the specimens 

 examined, occupied the posterior portion of the stomach, with 

 branches radiating from the muscular papilla into the lobes, and 

 undoubtedly reminds one of what Fischer" described as a body 

 shaped like the screw propeller of a boat. 



The digestive gland or liver (PI. ii, fig. 2) is a large organ 

 lying around the stomach, and covering the greater portion of it. 

 The right lobe (PI. iii, fig. 12, R.L.) spreads over the right and anterior 

 sides, and projects over the anterior adductor muscle, while the left 

 lobe (PI. iii, fig. 12, L.L.) covers the left and ventral sides and projects 

 posteriorly for some distance under the caecum of the crystalline 

 style. The large bile duct, with branches ramifying the right lobe 

 (PI. iii, fig. 12, B.Dt.), enters the cardiac part of the stomach on the 

 right anterio-lateral side, and the small bile duct, though of no 

 inconsiderable size, ramifies the left lobe (PI. iii, fig. 12, B.Dt'.), and 

 enters the small middle cavity situated between the cardiac and 

 pyloric portions. 



Solen siliqua, L. 



The alimentary canal (PI. ii, fig. 3.) is in all its important points 

 similar to that of S. ensis, but differs somewhat from it in detail. 



The oesophagus is straighten The stomach is similar to that 

 in S. ensis, but the divisions are more pronounced. The cardiac 



(5.) Manuel d. Conchyliologie, 1S87, p. 41. 



