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A MONOGRAPH OF THE GENUS 

 TELLINA. 



By SYLVANUS HANLEY, B.A., F.L.S., Etc. 



Char. Gen. Testa bivalvis, cujus latus posticum aut plicatura 

 irregulari radiante tumescit, aut cardo ejus dentem dentesve cluos 

 laterales ostendit ; dentes primarii duo, vel in utraque, vel in altera 

 valvula ; margo ventralis nunquam crenatus ; pallii cicatrix maxime 

 sinuata ; nymphae hand prominentes. Ligamentum externum. 



There are few genera whose definition is more difficult than that 

 of Tellina. The typical species with a strong fold or umboual ridge 

 and two distinct lateral teeth, cannot indeed be confounded with 

 the shells of any other genus ; but the whole of the aberrant divi- 

 sion, in which the fold is oftentimes nearly obsolete and the hinge 

 always devoid of lateral teeth, require the strictest examination, so 

 closely do they approximate to Sanguinolaria and Psammobia. 

 Lamarck himself has included several species of this division in 

 Psammobia and Psammota?a (the latter genus abolished by the 

 unanimous agreement of all conchologists) ; but the authority of 

 Deshayes gives weight to my own opinion, of the necessity of their 

 annexation to Tellina. The externally projecting nymphal callo- 

 sities which support the prominent ligament, characters which are 

 universal throughout Psammobia, are never present in Tellens of 

 this division. I may remark moreover, as a further assistance to 

 the discrimination of those closely allied genera, that the inclina- 

 tion of the line which unites the posterior muscular impression to 

 the parallel scar is ascending in those aberrant species which most 

 nearly approach Psammobia, whilst it is descending in that genus. 

 I speak more particularly of Psammobia, as there exists in some of 

 its species a fold almost equally profound (but symmetrical) with 

 that of the majority of the Tellina;. This does not exist in San- 

 guinolaria, of which I regard Rosea and not Ilugosa as the type. 



Certain Donaccs, devoid of crenulated margins, might probably 



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