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Note on the Subgenm Limea, Bronn. 

 By JOHN LYCETT, Esq. 



READ 28TH AUGUST 1855. 



THE present note is intended to direct attention to a peculiarity 

 connected with the external surface of Limea, trivial in its zoo- 

 logical importance, but which is calculated from its persistency 

 to be a useful aid to the palaeontologist in the absence of hinge 

 characters. 



The subgenus Limea has hitherto been distinguished from 

 Lima solely by the presence of a series of parallel teeth upon 

 each side of the hinge-plate, a feature which cannot be ascer- 

 tained in the majority of specimens ; and the only British species 

 of Limea hitherto described has so little in its general aspect to 

 separate it from the young condition of Lima duplicata (a shell 

 which is associated with it in the same beds), that any clear ex- 

 ternal distinction which can be ascertained between them is 

 worthy of notice, more especially when it will also be found to 

 characterize Limea as a subgenus. 



It is in the auricles that the distinctive feature resides, and it 

 is immediately connected with the hinge-plate beneath : it will 

 be found that the radiating lines which usually ornament the 

 surfaces of the auricles in the Pectens and Limse also exist in 

 Limea, but that in the latter they abruptly disappear towards the 

 outer angle of each auricle, leaving a small triangular smooth 

 area, which is traversed transversely downwards and inwards by 

 a few elevations ; these are placed immediately over and corre- 

 spond to the grooves which separate the teeth upon the hinge- 

 plate. In all well-preserved specimens this kind of surface is 

 visible upon one or both of the auricles, its distinctness depend- 

 ing upon the condition of the specimen with reference to fossi- 

 lization and the greater or less prominence of the internal 

 features. 



Limea duplicata is abundant in the shelly oolite of Leek- 

 hampton Hill ; there is also another more ornamented but un- 

 described species higher in the same formation, and found at 

 many localities in the upper Ragstones of the Cotteswold Int'i - 

 rior Oolite. The peculiarity of the auricles is observable equally 

 in both these specie. 



VOL. II. 



