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APPENDIX. 



During the progress of my work on the British Carboniferous Lamellibranchs, 

 species new to Great Britain, or hitherto undescribed, have from time to time 

 occurred. Some of them were described and figured in papers published in the 

 ' Quarterly Journal ' of the Geological Society and other journals, but several others 

 are now published for the first time. It has been found necessary to refer some of 

 these new species to six genera not mentioned in the body of the work, four of the 

 six being genera which have not hitherto been recognised in rocks higher than the 

 Devonian, namely, Megambonia (Hall), Palseoneilo (Hall), Spathella (Hall), and 

 Paracyclas (Hall). One species is referred to Pachypteria (deKoninck), and it has 

 been necessary to create a new genus (Nothamusium) for a number of specimens 

 referable to two species. 



Family OSTRBID^E. 

 Genus Paohypteeia, de Koninck, 1885. 



Generic Characters. — Shell of medium size, sub-oval, slightly inequivalve, and 

 oblique. Cardinal border straight. No ears. Umbones indistinct. 



Interior. — Hinge edentulous; left valve with a shallow pit below the umbo 

 corresponding to a tubercle in the right valve (de Koninck). The muscle-scar is 

 placed laterally and bounded by an almost circular crest. 



Exterior. — The surface is ornamented with numerous fine imbricating lamellae. 



Observations. — De Koninck established this genus for a single species which he 

 had previously described as Ostrea, thinking it had more affinity with the Aviculidas 

 than with Ostrea. I am at a loss to understand why he considered the shell to 

 possess ears, the concentric lines of growth of the valve passing up directly to the 

 hinge-line and terminating there. It seems to me, judging from the characters of 

 the shell, that his original view of its affinity to Ostrea was the more nearly 

 correct. I think he was wise to found a new genus for the shell, but the name is 

 an unhappy one, as there is no wing or projection, and the shell is not very thick. 



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