272 
The American Geologist. 
May, 1890 
larly those in Lower Silurian localities of the west and [north- 
west, will pay more attention to these fossils so that a] mono- 
graphical study may soon become practicable. 
Modiolopsis oblonga, n.sp. 
Fig. 1. Modiolopsis ohlonga,n. ^^.,\]t\ci\,^\aie horizon of the Cin- 
nati group, at Covington, Ky. a. A very perfect cast of the interior 
of a right valve of this species, preserving a little of the shell, and ex- 
hibiting most of the distinctive features of the species, h and c. End 
and cardinal views of same to show convexity. 
Shells above the medium size, moderately convex, elongate, 
the length more than twice the width, the posterior end a little 
the widest, anterior end small, contracted in front of the beaks, 
the upper portion slightly concave, the lower part narrowly 
rounded. Basal margin slightly convex or nearly straight, in 
the central half, and gently curved upwards at the ends. I^ Pos- 
terior margin obliquely subtruncate, with point of greatest ex- 
tension in the lower half where the curve is sharp. Junction 
of cardinal and posterior margins subangular, the two sides 
meeting at an angle of 120°. Cardinal margin very gently ar- 
cuate, long, the length behind the beaks equaling nearly three- 
fourths of the entire length of shell. Beaks small, depressed, 
scarcely elevated above the hinge line ; situated one-eight of 
the greatest length of the shell from the anterior extremity. 
Umbonal ridge subangular near the beaks, but becoming near- 
ly or quite obsolete before reaching the middle of the valve. 
Cardinal surface flattened. General surface of valves moder- 
ately convex, with greatest convexity in the anterior third. 
