310 
PALAEONTOLOGY OF NEW-YORK. 
Dorsal valve moderately and evenly convex with a well-defined low 
rounded mesial fold; beak, and margin of the valve in the middle, 
slightly arched. Area narrow at the sides, but having the width of a 
line in the middle. 
Surface marked by from sixteen to twenty plications on each side of the 
mesial fold and sinus : these plications are rounded and well defined; 
about eight of them reach the apex on the ventral valve, and the re¬ 
mainder coalesce with the angular border of the area. In perfect spe¬ 
cimens the entire surface has been covered by fine concentric undula¬ 
ting striae, which are crossed by fine radiating' striae. The remains of 
these, upon some of the silicified specimens, give a granulose surface. 
The length of full grown individuals is a little more than three-fourths 
of an inch, with a width of about an inch and three-eighths : the height 
varies from three-fourths of an inch to a little less. 
I have before me more than a dozen specimens from near the Falls of the 
Ohio or from Charleston landing, among which there is very little variation in the 
general features. The smallest individual of these has a length of a little more 
than half an inch. 
Dr. Owen first noticed this species in his Report in 1839. In 1841, I re¬ 
ceived specimens from him with this name attached ; and during many years, so 
far as I know, the specimens from the Falls of the Ohio and from Charleston 
landing were the only ones distributed under this name. In his Catalogue of Spe¬ 
cies, appended to the Geological Report of Wisconsin, Iowa and Minnesota, page 
628, Dr. Owen cites as localities “Pine creek; Davenport; below Rockingham; 
New-Buftalo ; Rapid creek ; Wapsinonox ;” and “ elsewhere in the United States, 
Columbus, Ohio; Charleston landing, Indiana ; Falls of the Ohio.” 
The figures 6 a, b ( ut cit.) appear to me to be of the typical form, and may have' 
been made from Indiana or Ohio specimens ; but certainly figures 2 and 2 a are 
not of the same species. I have not seen specimens from Pine creek er elsewhere 
in Iowa, which I regard as identical with those of Charleston lauding, although 
such may occur. I can only suppose that the similarity of form may have misled 
Dr. Owen, and induced this reference ; but I believe it will be more just and 
more satisfactory to retain the name 8. euruteines for the species to which it was 
originally applied by Dr. Owen himself. 
