FAMILY 3. SOLENACEA. 43 



The genus Solen of Lamarck presents such a diversity of form and 

 character, that we are induced to follow the plan proposed by Sowerby, 

 of retaining in it only those species which have narrow, linear shells, 

 with the umbones at one end, commonly called " Razor Shells." This 

 arrangement allows us to remove several species, hitherto involving 

 much confusion, to the Nymphacea, thus showing the propriety with 

 which that family might have been placed immediately after the Solena- 

 cea. But in attempting this, so much difficulty arises in disposing of the 

 Myaria and Mactracea, that we must be content to allow the Nymphacea 

 to remain in the situation assigned to them by Lamarck. 



The shell of the Solenes may therefore be described as equivalve, 

 linear, subcylindrical, very inequilateral, and gaping at both ends, the 

 anterior of which is somewhat truncated or rounded. The cardinal teeth 

 are small and variable, the hinder one sometimes bifid, and generally 

 recurved ; there is also a lateral tooth in some species. The muscular 

 impressions are distant from each other : the anterior one is ligulate, 

 placed under or behind the umbo ; the posterior is irregular and nearly 

 oval. The palleal impression is very long, and rather straight, divided at 

 the posterior end into two branches. 



The Solenes are found abundantly in all parts of the world, but espe- 

 cially on our own coast ; they, however, vary so little, that the differ- 

 ence of locality is scarcely discoverable from the appearance of their 

 shells. 



Examples. 



PL XXV. Fig. 1. 



Solen truncatus, Sowerby, Genera of Shells, No. 32. 



PI. XXV. Fig. 2. 



Solen vagina, Linmeus, Syst. Nat., p. 1113. Lamarck, Anim. sans 

 vert., new edit., vol. vi. p. 53. Enc. Me'th., pi. 222. f. 1. De Blain- 

 ville, Manuel de Malacologie, pi. 79. f. 2. 



G 2 



