222 PALEONTOLOGY OF KENTUCKY. 



NuCUla neda, HAM. AND WIIITKIKLD. 



Plate V., figures 5 and 6. 



Nucula neda, H. and W. 24th Eeg. Kep., p. 1911872. 

 Nucula neda, H. and W. 27th Reg. Rep., pi. 11 1875. 



Shell cuneiform, sub-trigonal, with the umbones ventricose ; the beak a 

 little more than one-third from the anterior end, prominent and incurved. 

 Cardinal margin sloping to the anterior and posterior extremities ; basal mar- 

 gin straight. 



The ast shows strong anterior and posterior muscular impressions, with 

 three or four umbonal muscular scars ; a narrow pedal scar just within the 

 cardinal line, anterior to the posterior muscular area, as usual in the genus 

 Nucula. 



The surface has been marked by fine concentric lines of growth. It is asso- 

 ciated with Nucula niotica, which it resembles in many features, but it differs 

 from it in several points, which are given in the description of that species. 



Formation and Locality. Occurs in the chert beds superimposed upon the hydraulic limestone of 

 the Devonian formation, around the Falls of the Ohio, in Kentucky and Indiana. 



NllCllla niotica. HALL AND WHITFIELD. 



Plate V., figures 2, 3 and 4. 



Nucula niotica, H. and W. 24th Regent's Rep., p. 190 1872. 

 Nucula niotica, H. and W. 27th Regent's Rep., pi. 111875. 



Shell small, obtusely cuneiform; the beaks prominent, incurved, with the 

 umbo inflated ; height from beak to base equal to three fourths the length of 

 the shell. Surface marked by fine, even, concentric striae, with sometimes 

 strong varices of growth. The internal casts show the evidence of strong, 

 anterior and posterior muscular im pressions, and three distinct umbonal pedal 

 muscles, seven or more posterior and five anterior teeth in a specimen of me- 

 dium size. Hall's description. 



We find three distinct Nucula in our rocks; two of the species have a cunei- 

 form sub- trigonal form, as shown in Prof. Hall's figures of Nucula neda and 

 niotica; they must, therefore, be the two species in question ; but which is neda 

 and which is niotica? Prof. Hall's descriptions and figures of both species may 

 answer to either one. There is only one point in the descriptions which may 

 decide the question ; this is the character of the respective umbones. Accord 

 ing to Hall, the umbo of N. niotica is inflated, and the umbo of the neda is 

 ventricose. Basing my identification of the two species upon this single point 

 of difference, I will try to point out a few more distinguishing features. Nu- 

 cula niotica differs from Nucula neda in the following characters : 



