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Additional Notice of the genus Tancredia (Lycett), Hettangia 

 (Turquem). By John Lycett, Esq. 



Read February 1853. 



At a meeting of the Cotteswold Naturalists' Club, held July 30, 

 1850, I had the honour to submit a memoir on the Testacea of 

 the middle division of the Inferior Oolite, accompanied by a 

 separate description of a group of small bivalve shells which 

 occur both in that rock and in the Great Oolite. This group I 

 proposed to erect into a genus, to be called Tancredia, a name 

 intended to commemorate a gentleman no longer, unfortunately, 

 a participator in our reunions. The fragility of the small shells 

 which exemplified the genus, together with the coarseness of the 

 investing stone, prevented my exposing the hinge of the left 

 valve so clearly as could be wished ; it was not therefore figured, 

 and the description of the hinge in that valve was defective ; but 

 the hinge of the right valve, together with the external forms of 

 three species, were faithfully rendered by Mr. Sowerby in the 

 plate which accompanied the memoir. The ' Annals and Maga- 

 zine of Natural History' for December 1850 contained the paper 

 in question, and it was incorporated with the Transactions of the 

 Cotteswold Naturalists' Club. The description of the hinge in 

 the right valve was substantially correct, but owing to an im- 

 perfect knowledge of the form, arising from the valves being 

 always found disunited, the term anterior was employed for 

 posterior, and vice versd. 



It is necessary to revert to these facts with precision, as during 

 the past year (1852) a French author of eminence, both as a 

 geologist and palaeontologist, M. A. Buvignier of Verdun, has, in 

 a new and splendid work on the geology of the department of 

 the Meuse, figured and described certain species of Tancredia 

 under the new generic name Hettangia, a name which he states 

 to have been chosen by M. Turquem, the discoverer of the genus. 

 The very superior manner in which the figures of that work are 

 executed leaves no doubt of the identity of the two genera ; the 

 five species which M. Buvignier has illustrated are from the Lias, 

 and bear the specific names Broliensis, Deshayesea, Turquemea, 

 longiscata, and Raulinea ? They are all distinct from the oolitic 

 species of the Cotteswolds. From this statement it is evident, 

 that in the absence of any other notice of the genus, my memoir 

 on Tancredia has a claim to priority, and the generic name which 

 I have chosen should be retained. More recently three addi- 



