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



to the oesophagael part, and projecting anteriorly to it. The pyloric 

 portion is not so deep, or so large, and rises at its posterior end. 



The right side of the oesophagael portion is smaller than the left 

 side, but is likewise bordered by a slight muscular ridge (PI. iii, fig. 7, 

 M.R.O.). The remaining portion of this side is large, but is not 

 divided in the same manner as the left half into cardiac and pyloric 

 portions. At the anterior lateral end, just above the cardio-oesophagael 

 ridge, it receives the large bile duct (PI. iii, fig. 7, B.DL), and, at its 

 posterior end on its ventral side, the intestine leaves it (PI. iii, fig. 7, 

 In.). The posterior end of the pyloric portion of the stomach con- 

 tracts to form the caecum (PI. iii, fig. 7, C.C.) containing the crystalline 

 style. The caecum is of considerable length extending in a posterio- 

 ventral direction through the proximal portion of the foot. 



The crystalline style (PI. iii, fig. 7, C.S.) is a long rod of a light 

 brown colour, traversing the whole of the caecum and the centre of 

 the stomach, in a course tending from the left to the right side, to the 

 anterior wall of the cardiac portion, where it generally has a hooked 

 termination. 



A transverse section of S. siliqna shows the epithelium (PI. iii, 

 fig. 10, Ep.C.) of the caecum to be very characteristic, and in marked 

 contrast to that of the adjoining intestine. It consists of long regular 

 columnar cells, with the nuclei generally situated nearer to the free 

 end than the proximal one. The nuclei are so regularly placed that 

 they appear to form a continuous ring around it. The cells stain 

 deeply at the free end, and carry a dense mass of long cilia. A 

 section through the anterior part of the caecum shows a curious 

 growth in the end lying near the intestine, where there is a fibrous 

 mass (PI. iii, fig. 10, x) coming from the caecal wall; this afterwards 

 gradually disappears. 



After the intestine leaves the stomach, it proceeds to the foot 

 where it makes a large number of closely lying convolutions (PI. ii, 

 fig. 2, C.In.), then describing a semi-circular course round the base 

 of the caecum, containing the crystalline style, and between the 

 transverse pedal muscles (PI. ii, fig. 2, T.P.M.), it passes along the 

 dorsal side of the caecum, on which it forms three large loops, and 

 shortly afterwards another one, then at the posterio-dorsal part of the 

 stomach, it turns, and as the rectum (PI. ii, fig. 2, R) pursues a 

 straight posterior course, passing through the pericardium, and encircled 

 by the ventricle. (PI. ii, fig. 2, V.) It continues over the posterior 

 adductor muscle (PI. ii, fig. 2, F.R.P.), and enters the cloacal cavity, 

 where, having become free, it terminates at the bi-lobed anus. (PI. ii, 

 fig. 2, A.) 



