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GLYCYMERIS. 



TESTA aequivalvis, crassa, transversa, utroque 

 latere valde hians ; epidermide nigra induta. 

 Epidermis testae marginem superans. Cardo 

 callosus, edentiilus. Nyinphai prominentes. 

 Ligamentum magnum, prominens, externum. 

 Impressiones musculares duae, irregulares, dis- 

 tantes, impressione musculi adhaerentis pallii 

 conjunctae. 



The Genus before us offers such an unusual assemblage of 

 characters, that we are surprized no one before Lamarck 

 should have described it as constitutino^ a Genus distinct 

 from all others. In conjunction with Ponop^sa and Solen^ 

 he forms with it his family of Solenacece; we should have 

 been pleased to have seen Solenimi/a also united to that 

 family, if, indeed, Glycymeris be well placed there; for 

 Soknimya appears to us to be much more nearly related 

 to Glycymeris than to either Ungulma or Amphidcsma. 



Shell equivalve, transverse, thick, gaping- widely at 

 both sides, in such a manner that the two valves can only 

 touch each other, when closed, at two points, at the hinge 

 and at the upper posterior edge. It is covered with a 

 strong black epidermis, which passes over the edge of 

 the shell where it becomes thinner and is of a lighter 

 colour : this epidermis is generally destroyed from the re- 

 gion of the umbones. There are no teeth to the hinge, 

 but the part to which the ligament is attached is a strong, 

 oblong, prominent callosity. The ligament itself is ex- 

 ternal, large and prominent. There are in each valve, 

 two distant irregular muscular impressions, which, though 

 distant, are connected by the impression of the muscle by 

 which the mantle adheres to the shell, in which there is a 

 small sinus close to the anterior muscular impression, in- 

 deed, the two lateral muscular impressions and the nius- 



