120 Records of the Indian, Muscuin. [Vol. XV. 



aud the lout aud the posterior retractor muscle of the foot of its side , 

 the glandular sac is comparatively wider than the non-glandular. The 

 walls of the non-glandular sac are generally seen applied to one another. 



The glandular sac ends in front of the posterior adductor muscle. 

 The nature of the communication between the glandular and non- 

 glandular sac is rather different in the three genera. 



In Lamellidens the glandular sac opens into the non-glandular by 

 means of a slit-like aperture on the dorsal aspect at its posterior end ; 

 a pigmented sac is found at the beginning of the ureter, open in front 

 but blind behind ; it lies on the outer side, having its outer wall fused 

 with the outer wall of the ureter and its inner wall lying free in the 

 cavity of the same ; the blind posterior end of the sac lies just in front 

 of the posterior adductor muscle, the inner surface of the sac is thrown 

 into irregular folds and gives the appearance of a broad meshed spongy 

 structure. 



In Solenaia the glandular portion is placed on the inner side of the 

 non-glandular sac. Towards the posterior end of the foot we get the 

 beginning of a canal bounded externally by the mantle, internally by 

 the non-glandular sac, above by the pericardial chamber and below by 

 the outer suprabranchial chamber ; the canal widens out as it passes 

 backwards. Behind the foot it forms a big sac lying on the outer side 

 of the glandular sac, while the non-glandular sac narrows down into a 

 small canal lying on the outer side of the posterior retractor nmscle of 

 the foot above the canal. Further backwards, the non-glandular sac 

 terminates in a small blind sac just in front of the posterior adductor 

 muscle. On reaching the under surface of the posterior adductor muscle 

 the canal comes to lie on its ventro-lateral aspect and ultimately becomes 

 continuous with the glandular sac by the disappearance of the septum 

 between the two. In the lumen of the canal, as it lies at the level of the 

 posterior retractors of the foot, there is an obliquely vertical septum, 

 attached above to the outer wall of the canal a little below the dorsal 

 aspect, and below to the inner wall a little above the ventral aspect. 

 The free anterior and posterior borders of the septum is deeply concave. 

 Above the upper attachment of the septum is an elongated aperture 

 through which the ureter comnrunicates with the canal. A similar 

 arrangement but rather different in details has been described in 

 Anodonta. 



In Physunio the glandular portion is placed on the inner side of the 

 ureter behind and both are flattened from side to side and slightly curved 

 on themselves, with the convexity outwards ; in this situation it is 

 separated from its fellow of the opposite side by the posterior retractor 

 muscles of the foot. The glandular sac communicates with the non- 

 glandular by an elongated aperture on its dorsal aspect, near the pos- 

 terior end. The glandular sac in this situation is divided into two 

 portions by an oblique partition, attached on the inner side to the ventro- 

 internal corner, on the outer side to the outer wall a little below the 

 dorsal aspect and behind to the outer wall just in front of the posterior 

 end of the sac ; it is free anteriorly. Of the two sacs thus formed the 

 upper one communicates with the ureter, while the lower one ends 

 blindly. 



