OF DENISON UNIVERSITY. 
59 
anterior projection is apparently acute, the lower margin forming an 
angle of 3o°-4o° with the hinge. The posterior wing is imperfect, 
but was probably slightly produced. Fig. 20 of Plate IV, is certainly 
wrongly restored, being, without doubt, the same species as the one 
first referred to. The relation to certain Chemung species, especially 
Pt. inoptatus, is very close. 
Leptodesina (?) scutella, sp. n. 
(Plate IV, Fig. 16.) 
A number of specimens of a little shell at first referred to Pteron- 
ites indicate a species belonging to section umbonata, but apparently 
distinct from any Chemung species. Sub-rhomboidal or nearly semi- 
ovate, anterior wing short, acute; body inclined about 50° to the 
hinge line, which it about equals ; posterior margin concave, upper 
angle produced, beak sub-anterior; surface gently convex, except the 
posterior wing, marked by equidistant lines of growth. With the 
above. 
Posiclonomya (Strehlopteria) fra^ilis, ”• 
(Plate VI, Fig. i.) 
The specinaens on which this species is founded differ from all 
Waverly species and all others known to me. The species may be 
compared with P. laterugata, but is less abate and has much more prom- 
inent beaks. 
The wings are almost too prominent for a member of the genus 
quoted and the presence of indistinct radiating striae passing over the 
coarse plications adds to the incongruity. 
The right valve is broadly oval or nearly circular, with the poste- 
rior ear considerably produced, anterior oue less distinct and shorter, 
margin below the ears a reniform broad curve resembling a circle ; 
surface of the valve rather flat, but somewhat suddenly elevated near 
the beak, which is acute and slightly projecting beyond the hinge ; 
hinge line straight, rather short ; surface marked by distant irregular 
folds and indistinct, fine, minute radiating striae. Height 29 mm ; 
