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SUPPLEMENT TO THE CRAG MOLLUSCA. 



the linear dimensions of the shells that occur in the Post Glacial valley deposit of 

 Stutton. 1 



This Corbicula lived here in association with a few other Molluscs which have disap- 

 peared from the British Isles, viz. Unio littoralis, Hydrobia marginata, Helix fruiicum, 

 and Helix ruderata, the two former of which have survived not far to the southward 

 of us, while the two latter have gone north, and are now found in Siberia and North 

 America, extending in a northerly direction up to the Arctic Circle. 



FRAGILLID^E. 



There are several small and tender bivalves in the Coralline Crag, figured and described 

 in the ' Crag Moll.,' which I think might be united in one family under the name of 

 Fragillida, separating them into genera or sections, the formula for each of which is here 

 given. The specific name annexed may be considered the type of each. 



Lepton, Turton {squamosum, Mont.). Shell thin, roundedly ovate or obtusely trian- 

 gular, equivalved, equilateral, slightly compressed ; surface of valves pitted or ornamented ; 

 beaks generally acute ; margins plain ; hinge with two lateral teeth in each valve, and 

 one small cardinal tooth. Palleal line simple; connexus cartilaginous. 



Lascea, Leach {rubra, Mont.). Shell small, thin, inequilateral, equivalved, oval or 

 oblong, closed, externally smooth or covered with fine lines of growth ; beaks depressed ; 

 hinge with two prominent lateral teeth and one small cardinal tooth; palleal line simple; 

 connexus cartilaginous. The animal is said to have a tubular prolongation in front of 

 the mantle. 



Bornia, Philippi {ovalis, S. Wood). Shell smooth, thin, ovate, or subtriangular equi- 

 valved, slightly compressed, closed ; hinge with two diverging teeth in each valve ; 

 palleal line simple ; connexus cartilaginous. 



iScacc/iia, Philippi {elliptica, Scac). Shell small, thin, ovate or elliptical smooth, 

 inequilateral, closed ; two cardinal teeth in one valve and one in the other ; palleal line 

 simple ; connexus cartilaginous. 



Scintilla, Deshayes {ambigua, Nyst). Shell ovately transverse, thin, equivalved, equi- 

 lateral, smooth, closed ; two teeth in one valve and one prominent obtuse tooth in the 

 other ; palleal line simple ; connexus cartilaginous. Sportella resembles this, but it has a 

 ligamentous connector. This latter I have not seen from the Crag, but it is not rare in the 

 Older Tertiaries. 



Kellia, Turton {sub orbicular is, Mont.). Shell thin, suborbicular, or slightly transverse 

 equilateral, smooth, closed ; hinge with two teeth in each valve, one before and the other 

 behind the connector ; palleal line simple ; connexus cartilaginous. 



1 The Stutton Post glacial deposit is in the low ground skirting the estuary of the Stour, opposite 

 Manningtree, and is not to be confounded with the well-known Crag locality of Sutton in the same county 



