RHYNCH0NEXLID2E OP THE GONIATITE LIMESTONE. . 357 
Leiorhynchus mysia. 
PLATE LVI. 
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. 
Leiorhynchus qnadricostata. 
PLATE LYI. 
Orthis qnadricostata : Vandxeii, Geol. Rep. Third Dist. New-York, p. 186. 1842. 
** “ Hall, Geol. Rep. Fourth Dist. New-York, p. 223, f. 2. 1843. 
Leiorhynchus qnadricostata : Hall, Thirteenth Report on the State Cabinet, p. 86. 1860. 
Compare Leiorhynchus multicosta : Id. Ib., p. 85. 1860. 
SAell 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. 
