UNGULINA. 



Daudin. 

 ^» 



TESTA suborbicularis, superne rotundata, aequi- 

 valvis, subaequilatera; valvis non hiantibus. 

 Dens cardinalis, in utraque valva, brevis, sub- 

 divisus: deiite minutissimo in altera adjecto. 

 Fovea ligamenti oblonga, mar<^inaiis, medio 

 angustato-divisa, Ligamentum semi-inter mini, 

 foveis insertum, hnpressiones musculares duse, 

 oblongse. Impressio musculi adhserentis pallii 

 intesrra. 



A Genus of bivalve shells, established by Daudin, and 

 adopted by Lamarck, but at present almost unknown in 

 this country. Lamarck does not appear to have known 

 the locality of the two doubtful species which he has 

 described, but our specimens are brought from Senegal : 

 we have good reason to think they are marine. In general 

 form and appearance these shells very nearly resemble the 

 Lucince; an examination of the muscular impressions will 

 easily distinguish them, for in Lucina the posterior mus- 

 cular impression is always of a more or less elongated 

 ligulate form : Lucina has, moreover, in general, two 

 lateral teeth, which Ungulina has not. Sometimes the 

 specimens of this latter Genus become elongated by age ; 

 but when young they are all nearly orbicular, and even 

 when of a more advanced age we think this circumstance 

 cannot be regarded as a good specific distinction, because 

 it appears, in the specimens we have seen, to have been 

 caused by some accident, with the nature of which Ave are 

 not acquainted. We therefore, in describing the general 

 form of this shell, rather approve of the term suborbicular, 

 than of longitudinal 3 its valves are equab nearly equi- 



