KHYNCHONELLID^ OF THE GONIATITE LIMESTONE. 357 



LeiorIi}iicIias niysia. 



PLATE LVL 

 Shell small, suborbicular ; valves subequally convex, with a few strong 

 plications reaching half way from the margin to the beak of the 

 shell. 



This species is distinguished by its small size, circular form, and proportionally 

 much stronger plications, of which there are at least three on each side of the 

 fold and sinus, terminating near the middle of the shell. In a few larger indi- 

 viduals, the plications have a greater extent. A single plication marks the sinus. 

 The length of the shell is usually less than three-eighths of an inch ; width a 

 little greater. One individual measures nearly a quarter of an inch in length. 



In a specimen of L, limitaris of the same size, the plications are scarcely 

 perceptible. 



Geological formation and locality. This species occurs in the Goniatite lime- 

 stone of the Marcellus shale, in Schoharie, associated with L. limitaris. 



Leiorh^nchus qnadricostata. 



* PLATE LVI. 



Orthit quadricoitata : VANrxEK, Gedl. Eep. Third Dist. New-York, p. 186. 1842. 

 - " Hall, Geol. Rep. Fourth Dist. New-York, p. 223, f. 2. 1848. 



Leiorhynchus qtiadricottata .- Hall, Thirteenth Report on the State Cabinet, p. 86. 1860. 

 Compare Leiorhynchut multicoita : Id. n>., p. 86. 1860. 



Shell broadly ovate, somewhat gibbous, with distinct mesial fold and 



sinus. 

 Ventral valve a little gibbous towards the beak ; sides nearly flat, with 



a wide mesial sinus. 

 Dorsal valve more gibbous than the opposite, greatest convexity in the 



middle of the valve ; mesial fold prominent. 

 Surface of mesial fold and sinus marked by three, four or five rounded 



plications, which bifurcate above. Sides of the valves obscurely marked 



by rounded plications, which become obsolete towards the margin, and 



sometimes this part of the shell is almost entirely free from any 



markings whatever. 



