I ... 





LAMKI 



611 



MAJOR /'/r 



CfrfcJopAortu m.i. r i i M. H, J87. Jour. Cin. Soc. Nat l! p. 36. 



I, right valve of Lgrodrtma major Ulrlch; 6, cardinal slope of name, x 2, showing the flap 

 radiating stria-; <-, Interior <>r u right v;il\v: <l. hinge of *ani<<, x 2; , left Aide of a cast of tin- Interior nf 

 same, showing tli<- mu-rular scars and palllal line with unusual distinctness; /, dorsal view of K.-IIIH-, slightly 

 enlarged: g, vertical section through a valve at the beak, showing ink-knew of hinge plale and why the 

 beaks la casts are widely separated; specimens from upper beds of the Cincinnati group at Clarksvllle, 

 Ohio. A, right valve of Lfrodetma acuminatum, var. inlermfdium, from the Trenton near Jturniii. K.-n 

 turky. i, dopial view of a cant of the interior of TecAnopAoru* rxtenuattu Ulrlch, x 2, showing the 

 united beaks, the flattening of the posterior dorsal edge and other feature*. 



Shell transversely subovate, unusually elongate for the genus, narrow poste- 

 riorly; length of three testiferous examples 17, 24 and 28 mm., greatest bight of 

 same (from beaks to basal margin) respectively, 11, 15 and 18 mm.; greatest thick- 

 ness snbcentral, somewhat greater than half the bight; anterior margin rounded, 

 most prominent immediately above the middle of the bight, often atraightened in 

 the upper half to the beaks; base broadly yet rather strongly convex; posterior end 

 long, somewhat attenuate, narrowly rounded at the extremity; cardinal outline 

 declining each way from the beaks, more or less concave behind them. Beaks rather 

 prominent, small, incurved, situated about one-fourth of the entire length from the 

 anterior extremity; umbones full, sharply rounded on the posterior side where the 

 -nrf;ice descends abruptly to the cardinal margin; behind the beaks the dorsuni is 



'oncave, then flat and finally low ridge-shaped; beneath, or rather in front of 

 them, there is an impressed line on each side which defines an elongated lanceolate 

 area. Surface nearly smooth, in one example exhibiting fine concentric stritr. All 

 of the testiferous specimens however have twelve or more, fine radiating lines on 

 fli" posterior umbonal ridge and cardinal slope. 



Hinge with six teeth in each valve, the four central ones much stronger than 

 the marginal pair. Muscular scars strongly impressed, the anterior adlm-t<>r-harply 

 defined on the inner side by a thin ridge running down from the hinge, narrowing 

 above and surmounted by deep supplementary sears; posterior .cMm-tor elevated 



