SOLEN. 



TESTA sequivalvis, elongata, subcylindrica, valde 

 insequilateralis, utraque extremitate hians, 

 antica brevissima, truncata vel subtruncata, 

 interdum rotundata. Cardo dentibus variis, 

 plerumque acutis, recurvisi interdum dente 

 laterali, elongate, uncinate. Impressiones mus- 

 culares distantes, antica ligulata, sub vel post 

 umbonem positc^ postica irregularis, subovalis; 

 impresslo muscularis pallii rectiuscula, lon- 

 gissima, postice bifurcata. 



In endeavouring to draw up a definition of this Genus we 

 have experienced much difficulty, on account of the very 

 great diversity of character exhibited by the shells which 

 have, by common consent, been hitherto united together 

 as Solenes. In No. XXV. of this work under the article 

 Sanguinolaria it will be seen that we have not hesitated to 

 separate from it several which had hitherto been associated 

 with it. We now think that all those whose anterior 

 muscular impression is placed before the hinge teeth, might 

 without impropriety be detached from it : some of these 

 would go to increase the Genus Psammobia, others form 

 De'Blainville's Genus Solecurtus, and those inwhich may be 

 observed an incrassated internal rib passing from the um- 

 bones toward the inferior edge, may form a well marked 

 and distinct Genus. Such a separation will much facilitate 

 the task of the learner in arriving at a knowledge of the 

 natural genera, and it will not be attended with any real 

 inconvenience, because it is very evident that Lamarck^s 

 " JSolenacees" must be brought close to his JVj/mphacees 

 Solenaires" in the natural system. Adopting this view of 

 the subject, we include in the Genus Solen only those which 

 are generally termed Razor Shells, whose anterior side is 

 very short, and whose anterior muscular impression is 

 placed immediately under or behind the beaks. 



