NIAGARA GROUP. 
109 
This fossil corresponds very closely with the Patella? implicala (Silurian Researches , 
p. 625, pi. 12, f. 14, a.). I had supposed it to be the young of fig. 3 ; but its oval form, and 
the lateral situation of the apex, preclude the idea. It occurs on the surface of the shaly 
laminae with other fossils, always presenting the appearance of a thin translucent scale. 
Locality —Rochester and Sweden in Monroe county. 
2. Lingula lamellata, n. s. — Oval, somewhat broader towards the base. Shell covered 
with concentric, slightly undulating, elevated lamella:, wrinkled at the sides, gradually rounded 
at the base. Beak sharp, scarcely elevated. 
Perfect specimens of this fossil are not of common occurrence. The surface is not striated, 
but the shell appears as if composed of concentric laminae with elevated edges. 
Locality —Lockport, Rochester, Sweden. 
3. Orbicula corrugata, n. s. — Orbicular ; surface strongly wrinkled, and covered with 
finer concentric undulating lines; muscular impression on the under valve very distinct, and 
often extending half way from the apex to the circumference. 
This fossil is easily distinguished from any other in the rock, by its orbicular form and 
wrinkled surface. I have seen one or two specimens which exhibit the two valves only par¬ 
tially separated, and there seems no doubt of the propriety of its reference to this genus. 
Locality —Rochester, Sweden, Lockport, Wayne county. 
4. Avicula emacerata (Conrad, Jour. Acad. Nat. Sci. Vol. 8, p. 241, pi. 12, f. 15).— 
Lower valve slightly convex, wider than high, finely radiated ; radii equal, diverging toward 
the margin, crossed by elevated concentric lines, giving the whole surface a cancellated ap¬ 
pearance. Upper valve smaller, nearly flat, plain, or with a few concentric lines, and some¬ 
times a few radii on the posterior wing; posterior wing acutely angular ; anterior one slightly 
rounded at the extremity, very short. 
From some specimens, it w r ould appear that the radii on the larger valve become obsolete 
with age, as several large valves have been seen without them. 
Locality —Lockport, Sweden. 
39. 
1 and 2. Euomphalus hemisphericus. 3. Cornulites arcuatns. 
