56 Records of the Indian Museum. [Vol. XIX, 



Comparing the general conformation of the body of the three 

 species under consideration we find that in 5. kempi, Preston, the 

 elongation has far more affected the anterior than the posterior 

 portion of the body, and that in 5. gravelyi the anterior and the 

 posterior portions are perhaps equally affected in the process. In 

 S. sp. from Japan the posterior portion of the body is comparatively 

 more elongated than the anterior. 



Although a large number of species of Solcn have been 

 described from their shells, only a few are known by their 

 animals. 



Considering the few species described by Bloomer and three 

 species of mine, it is premature, at the present moment, to attempt 

 to group the various species of Solen into sections according to the 

 conformation of their soft parts. And the anatomical conditions 

 may, if possible, be further co-related with the peculiarities of the 

 shells. For the present, a division of the above species into 

 sections may be provisionally suggested as follows : — 



Section I. Body elongated equally both anteriorly and pos- 

 teriorly. 



Types : 5. vagina, S. gravelyi. 



Section II. Body elongated more anteriorly than posteriorly. 



Type : 5. kempi. 



Section III. Body elongated more posteriorly than anterior- 



ly. 



Types : vS. sp. from Japan, 5. dolerscoti. 



Subgen. Solcna, Browne (1756). 



1854.. Hypogella, Gray, An)i. Mag. Nat. Hist. (2) XI\', p. 23. 



1858. Subgen. Solena, Browne, Adams, Gen. Recent Mollttsca, II, 



p. 342. 

 1887. Sect. Hypogella, Gray in Fischer, Man, de Conch, p. iwo. 



The anatomy of Solena rudis, Adams, has been studied by 

 Bloomer (11). The anatomical peculiarities in which it differs 

 from the species of Solen have sufficient grounds for ranking the 

 present animal as the type of a subgenus already erected for it. 

 The following diagnosis has been drawn from Bloomer's anatomical 

 work on 5. rudis : — 



Animal. Body elongated with rounded anterior and posterior 

 margins. Pedal aperture confined to the anterior margin and 

 guarded by pedal valves. Siphon a single piece. A pair of valves 

 in the proximal portion of the siphon in both the apertures. 

 Anterior adductor muscle broad and deep (more or less oval in 

 shape). Posterior adductor muscle of the same size, being much 

 larger than the retractor pedis posterior muscle at its insertion. 

 Foot more or less flattened, but somewhat swollen towards the 

 distal end. Fibres of the retractor pedis anterior muscle passing 

 between the longitudinal muscles and the pedal integument 

 Labial palps relatively short and wide, the anterior lip being sepa- 

 rated from the posterior end of the anterior adductor muscle by 

 a short interval. Gills heterorhabdic and plicate, alternate inter- 



