XIII. ON THE ANATOMY OF CERTAIN INDIAN 

 UNIONIDAE. 



By Ekendranath Ghosh, M.Sc, M.D. 

 (With Plate XVI.) 



Introduction. 



The genera and species of Unionidae discussed in this paper are : — 

 Lamellidens marginalis (Lamarck), Solenaia solenijormis (Benson), 

 Physunio ferrugineus and Ph. micropfer aides, Annandale. These species 

 resemble one another so closely in anatomical structure that I have 

 considered it best to treat them together in a comparative manner. 



The method of study was (1) simple dissection of the soft parts of the 

 animals after removal from the valves, checked by (2) longitudinal 

 (sagittal) section of the entire animal and (3) serial transverse section 

 of the whole animal (into thin slices, 2-4 mm. thick) from one end to 

 the other. The gills were studied microscopically after sectioning by 

 the usual paraffin method. They have been specially studied with 

 reference to the formation of the marsupium. 



As regards the materials, the specimens of Lamellidens were procured 

 from tanks about Calcutta, while the others were received from the 

 Zoological Survey of India through the kindness of Dr. Annandale. 



I. Mantle-lobes. 



The mantle-lobes are free from each other from the antero-dorsal 

 aspect of the anterior adductor muscle down along the ventral 

 margins to the posterior margin as high as the postero-dorsal aspect 

 of the posterior adductor muscle. Behind, the two lobes are joined 

 to one another between the exhalent and inhalent apertures by a 

 horizontal shelf formed by their fusion with the free dorsal margins 

 of the outer lamellae of the outer gills and of the other lamellae of the 

 gills to one another. The point, of fusion of the mantle-lobes is placed 

 just at the antero-dorsal aspect of the anterior adductor muscle in 

 Lamellidens and Solenaia, but at a higher level in P. jerrmjinens and less 

 so in P. micropteroides ; further, this point forms the most anterior 

 end of the lobes, and in the case of Lamellidens and Solenaia is placed 

 at the level of the ventral border of the anterior adductor muscle. A 

 small gap between the margins of the mantle-lobes is left above the 

 posterior adductor muscle, exposing the dorsal wall of the rectum in 

 both Lamellidens marginalis and Solenaia solenifonnis. This gap is 

 absent in both species of Physunio. 



Above, each mantle-lobe is fused with the body-wall, the line of 

 separation passing along the ventral aspect of the anterior adductor 

 muscle, the base of the anterior lip of the mouth, and the attached 

 dorsal margin of the anterior half of the outer labial palp ; the line of 



