1920.] E. Ghosh : Anatomy of the Solenidae. 51 



VascuIvAR vSystem. The position of the heart varies some- 

 what in different genera. It may occupy the anterior, middle or 

 posterior portion of the pericardial chamber. 



Nervous System. Some difference has been noted in the 

 position of the viscero-parietal ganglia varying from beneath the 

 bifurcation of the retractor pedis posterior muscle to the antero- 

 ventral aspect of the posterior adductor muscle. There are also 

 some minor differences in the origin, number and distribution of 

 the nerves from the various ganglia. 



Classification. 



The family Solenidae may be divided into three subfamilies, 

 two of which form natural assemblages of genera having a number 

 of important characters in common. The genus Novaculina, 

 Benson, differs so much from either of the two other subfamilies 

 that it is best placed in a subfamily of its own. 



Subfam. SOLENINAE. 



1858. Subfam. Soleninae, subfam. Pharinae (pars), Adams and Adams, 



Got. Recent Mollusca, pp. 340, 342. 

 1862. Solenaria, Siliquaria (pars) Bronn, Tliiei'-Reichs. Malacozoa 



Acephala, III (2), p. 476. 



The present subfamily includes the typical genera of the 

 famil^^, presenting a narrow, elongated body, compressed from side 

 to side, and a Solen type of intestine. It may be diagnosed as 

 follows : — 



Animal. Body elongated, narrow in depth and compressed 

 laterally. Pedal aperture variable in extent. United ventral 

 margins of the mantle lobes forming a very narrow elongated 

 surface. No cruciform muscle. Siphons either fused in a single 

 piece with two siphonal canals, or completely free from each other. 

 No siphonal space (p. 48) posteriorl3^ A narrow, elongated 

 cylindrical foot extending horizontally forward through the pedal 

 aperture. Retractor pedis anterior muscle bifurcated or not 

 {Solena, Pharella, Cultellus) and generally directed upwards and 

 forwards. Protractor pedis muscle rudimentary or absent. Gills 

 simple or plicate. Intestine arising directly from the pyloric 

 stomach and consisting of two limbs. Viscero-parietal ganglia 

 beneath the bifurcation of the retractor pedis posterior muscle 

 or under the posterior adductor muscle (Pharella). 



The subfamily forms a natural group by itself. Further 

 study of the soft parts of the animals of the present subfamily 

 will perhaps raise it to the rank of a distinct family. 



Gen. Solen, lyinne. 



1782-93. Solen (pars), Linne, Sysf. Nat., ed. XIII (edited by Gmelin), 



p. 3223 (pars VI). 

 1858. Solen, Adams and Adams, Gen. Recent Mollusca, II, p. 340 ; III, 



pi, xcii, fig. I. 

 1874. Solen (pars), Ree\-e, Conch. Icon., XIX. 



