11^') Records of the Indian Miiseuvi. [Vol. XV, 



Loop of tlio Intestine. L. mnrgiiialis. Solcnaia solcniformis. Physunio 



(2) Second loop, pass- 

 ing forwards and 

 upwards to the 

 dorsal aspect of 

 the visceral mass. 



(3) Third loop, pass- 

 ing downward 

 and backward 

 aiid lying behind 

 the second loop. 



Course nearly 



straight, half the 

 first loop in length. 



Course slightly curv- 

 ed, about half the 

 length of the first 

 loop. 



Course curved with 

 convexity up- 

 ward and back- 

 ward, about the 

 same length as 

 the first loop. 



Course like that of the second loop and slightly longer than the 

 same. 



(4) Fourth loop, pass- 

 ing forward and 

 lying beneath the 

 posterior portion 

 of the first looj). 



(r>) 



Fifth loop, pass- 

 ing backward and 

 downward. The 

 junction between 

 the fourth and 

 fifth loops cross- 

 ing the first loojj. 



Course straight, 

 slightly upward 

 and al)out half 

 the length of the 

 first loop, lies be- 

 low the first loop. 



Course straight, 

 slightly shorter 

 than the fourth 

 loop, lying above 

 the first loop. 



Like Lmndlidens but Course rather short, 

 nob upward (or less than half 



very slightly so). the length of the 



first loop. 



Course straight, 

 about half the 

 length of the 

 fourth loop, ly- 

 ing above the 

 first loop. 



f'ourse about half 

 the length of the 

 fourth loop. 



(6) Sixth loop, pass- 

 ing uj^ward and 

 forwai'd to end 

 in the rectum. 



Al)out the same 

 length as the fifth 

 loop, lying above 

 the fifth loop. 



Very short, about half the length of the 

 fifth loop. 



(e) The rectum, is recoonised by a thick, prominent typhlosole from 

 the ventral wall Beginning in the visceral mass, it passes forwards 

 and upwards to reach the space between the digestive gland and the 

 stomach i)i front and the pericardial sac behind. It then passes verti- 

 cally upwards and at once bends backwards to enter the pericardial 

 chamber ; it passes through the chamber, being surrounded by the 

 ventricle, and leaves the chamber at its posterior end. Lastly, the 

 rectum passes backwards along the dorsal aspect of the posterior adductor 

 muscle and ends in the anus placed at the summit of a conical papilla 

 projecting into the cloacal chamber from above the posterior adductor 

 muscle. Tn LnmeUide7is the course of the rectum through the pericardial 

 chamber is straight and horizontal ; furthermore, it presents two bulb- 

 like swellings in front of and behind the ventricle ; the conical papilla 

 is flattened from side to side and the anus is a longitudinal slit with two 

 lateral dentate margins which ordinarily keep the aperture closed. In 

 Solenaia it is similar to that in Lamellidens in all respects except that 

 the swellings are absent. In Physunio the course through the peri- 

 cardial chamber is oblique (upwards and backwards from in front) and 

 is slightly curved posteriorly with the convexity upward after it has 

 left the pericardium ; there is no bulbous swelling in the wall and the 

 amis is more or less rounded, being surrounded by a fringe specially 

 prominent on the dorsal aspect. 



