216 PALEONTOLOGY OF KENTUCKY. 



form tooth in the left valve, and a corresponding cavity in the right ; no lateral 

 teeth exist. Anterior muscular impression sub-circular, situated within the 

 anterior extension of the shell ; posterior impression large and superficial, sit- 

 uated near the cardinal border ; pallial line entire. Ligament external, 

 attached to the thickened margin of the shell. 



This genus is allied to Modiola, Modiolopsis and Cypricardites, but differs 

 from Modiola in the toothed hinge ; from Modiolopsis in not having lateral 

 teeth, and from Cypricardites in general aspect. Modiomorpha concentrica 

 may be considered the type of this genus. 



Modiomorpha affinis, HALL. 



Modiomorpha alia, in part (Conrad), Hall. Pal. N. Y., Vol. 5, part 1, Plates and Explanations pi. 37, figs 



13 and 141883. 

 Modiomorpha affinis, Hall. Pal. N. Y., part 1, page 2841885. 



Shell large, robust, obliquely ovate, arcuate ; length about one-third greater 

 than the height; basal margin straight or slightly arcuate, curving rather 

 abruptly both at the anterior and posterior extremities; posterior margin 

 abruptly curving below and more gently forward to cardinal margin ; cardinal 

 margin arcuate from the beaks to the post-cardinal extremity. Anterior end 

 short, scarcely denned ; narrow, declining from the hinge-line and regularly 

 rounded below. 



Valves convex, very gibbous in the middle and umbonal region ; depth more 

 than half the height of shell. The umbonal elevation extends from the beaks, 

 curving above the middle to near the post-basal margin, forming an undefined 

 arcuate ridge. 



Hinge-line oblique, extending more than one -third the length of the valves. 

 Beaks small, sub-anterior, and closely incurved. 



Test comparatively thick, marked by fine concentric striae, which are fascicu- 

 late and pass into strong abrupt ridges upon the umbonal and anterior portions 

 of the shell. Interior unknown. 



An individual of average size, among the specimens of this species in my 

 collection, measures as follows : length, twenty -one lines ; height, sixteen lines, 

 and thickness, eleven lines. 



This form resembles Mod. alta, but is more elongate, distinctly arcuate ; 

 the anterior end is narrower below the beaks ; the posterior end is more pro- 

 duced, and curving more abruptly forward in the upper part, with the post 

 cardinal angle rounded. The anterior end is less produced than in typical 

 forms of Mod. mytiloides. 



Formation and. Locality. Found in the cherty layers superimposing the hydraulic limestone of 

 the Devonian formation, in Jefferson county, Ky., and in Clark county, Ind. Almost all my specimens 01 

 this and other species of Modiomorpha were found in the cement quarries at "Watson Station, in Clark 

 county, Ind., about six miles distant from the Falls of the Ohio, 



