brii SYNOPSIS OF GENERA. 



EUCHONDRIA, Meek. 



Am. Jour. Sci., 3d ser., vol. vii, p. 445. 1874. 

 [Type Pecten neglectiis, Geinitz.] 



" Mr. Meek states, in a letter to one of the editors, that he proposes to 

 institute the genus Euchondria for Pecten negledus of Geinitz, on account of its 

 peculiar hinge as illustrated by figure 7c, plate xxvi, in vol. v, of the Illinois 

 Geological Report." 



This genus as illustrated by Mr. Meek {ut cit.) has an unsymmetrical sub- 

 rostral cartilage-pit, and the crenulations on the two sides are unequal. 



If these characters can be shown in other specimens and other species, it is 

 probable that this genus will prove to be clearly distinct. At present it can 

 include only a single species, E. negleda. 



The figures of this species given in the Palaeontology of Illinois, are intro- 

 duced for comparison with Pernopeden and Crenipeden. 



Figs. 4, 5. EncHONDRiA neolbota (Geinitz, sp.). A i-eproduction of tigs. 7c and 

 7a, of plate xxvi, Geol. Surv. Illinois, vol. v. Fig. 4, a right valve, enlarged to 

 two diametei-s. Fig. 5, an enlargement of the hinge. Coal measures. Illinois. 



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