APPENDIX. 



THE ANATOMY OF THE COMMON SOLEN OF THE CHILKA LAKE.— 

 ? A DWARFED FORM OF 5. FONESI, DUNKER. 



By Ekendranath Ghosh, M.Sc, Asst. Professor of Biology, 



Medical College, Calcutta. 



The anatomy of Solen fonesi has been described briefly by Bloomer ', but he gives 

 few details of the internal structure and does little more than compare the foot, 

 mantle, etc., with those of S. vagina. No detailed account of S. vagina is available 

 in Calcutta and there are no specimens in spirit in the Indian Museum. It has there- 

 fore seemed best merely to describe the different organs of the form from the Chilka 

 Lake and leave it to other malacologists more favourably situated as regards litera- 

 ture and material to decide whether the identification is correct. 



In one point this form differs markedly from that described by Bloomer, viz., in 

 the entire absence of pigment on the external surface of the foot and mantle. 



SHELL. 



Shell thin, translucent, very brittle, with a brownish epidermis, corroded in its 

 upper anterior portion (upper anterior quadrant), length about three and a half times 

 the breadth ; anterior margin straight and directed from above a little forwards, wifi 

 a rounded antero-inferior angle ; posterior margin straight and nearly vertical ; a 

 single narrow elongated umbonal tooth just behind the antero-superior margin in the 

 right valve. 



Anterior adductor impression elongately triangular, with the base oblique and 

 directed in front ; anterior retractor impression small, rounded and just below the 

 anterior end of the anterior adductor impression. Posterior adductor impression 

 small, rounded, just a little in front of the postero-superior angle ; posterior retractor 

 impression rounded, of the same size as that of the posterior adductor and placed 

 just in front of the latter. 



ANATOMY. 



In preparing the following description I have had recourse to the following 

 methods : — 



(i) Two relatively large specimens have been dissected ; the structures have been 

 followed with the naked eye and with the help of the dissecting microscope. 



(2) Three medium-sized specimens, taken out of their shells, have been dehydrat- 

 ed in absolute alcohol, and cleared in clove oil. The mantle-lobes, gills, and the 



1 Journ. Malac. Soc. London, VII, p. 18 (1906). 



