PELONATA. 143 



the chamber, in a deep sigmoidal curve, and, bending 

 upwards, extends in a straight line to the cloaca. This, 

 the rectal portion, is considerably wider than the pyloric 

 extremity, and its walls are thin and membranous. 

 The anus (PI. XLVII, tigs. 1-3) is a wide orifice with 

 the margin reflected and divided into about twenty 

 rounded lobes or denticulations. In the pyloric por- 

 tion the mucous membrane is stout and is produced 

 into a ridge along the left side, as evinced by a dark, 

 groove-like line seen on the surface, similar to that 

 observed in Styel<i. The mucous membrane of the 

 stomach is likewise raised into numerous, close, regular, 

 longitudinal plicae. The lining of the oesophagus 

 appears to be smooth. 



The whole of the alimentary tube lies within a fold 

 of the lining; membrane, and thus becomes attached to 



O 



the right-hand wall of the pallial chamber. The 

 greater portion of the intestine merely bulges out this 

 membrane ; but the stomach and oesophagus project 

 further into the pallial chamber, being, to a certain 

 degree, suspended as it were by the infolding mem- 

 brane. These organs are further steadied in their 

 position by numerous, soft, tubercular nodules, similar 

 to those associated with the genitalia in Styela, which 

 stud both sides of the mantle at the lower extremity. 

 The largest of these somewhat enigmatical bodies are 

 found at the bottom of the pallial chamber, but they 

 extend some little way upwards, diminishing in size 

 and number. 



The biliary duct (PI. XLVII, fig. 1), which is single 

 in this form, lies in a fold of the lining membrane, 

 similar to that in Styela ; it passes from the intestine 

 to the right side of the pyloric end of the stomach. 

 Before terminating, the duct receives a twig or two 

 from the surface of the stomach, so that, in this genus, 

 the liver is apparently not confined to the intestine, 

 but is also partially spread over the stomach. The 

 ultimate twigs divide dichotomously with considerable 

 regularity ; they are occasionally enlarged so as to 



