82 CLASS I. TR0P10P0DA. ORDER I. BIMUSCULOSA. 



oblique. The hinge has sometimes two divergent teeth, sometimes none ; 

 in one valve there are two lateral teeth, one on each side, the anterior of 

 which is situated near the hinge, and in the other there is but one ; these 

 however are often obsolete. 



The muscular impressions of attachment are distant from each other, 

 and the anterior one is prolonged in the form of an elongated or ligulate 

 band. The interior of the shell exhibits a simple palleal impression, very 

 strongly marked, and is often punctured with small holes or striae. 



Examples. 



PI. LIX. Fig. 1 . 



Lucina punctata, Sowerby, Genera of Shells, No. 27. 

 Venus punctata, Linnaeus. / 



Cytherea punctata, Lamarck. 

 Lentilaria punctata, Schumacher. 



PI. LIX. Fig. 2. 



Lucina Childreni, Gray, Annals of Philosophy, 1824. Sowerby, Ge- 

 nera of Shells, No. 27. 



PI. LIX. Fig. 3. 



Lucina Jamaicensis, Lamarck, Anim. sans vert., new edit., vol. vi. 



p. 223. Sowerby, Genera of Shells, No. 27. 

 Venus Jamaicensis, Chemnitz. 



DON AX, Linnaeus. 



Testa transversa, aequivalvis, inaequilateralis, latere antico brevissimo, 

 obtusissimo. Dentes cardinales alterius valvae duo, alterius uni- 

 cus, superne bifidus ; laterales duo vel unus, plus minusve remoti. 

 Ligamentum externum, breve, plerumque bipartitum, partim post 

 umbones positum. Impressio muscularis pallii sinu magno. 



