OF DENISON UNIVERSITY. 
39 
ton, in the following terms : Cardiomorpha ovata. “Shell ovoid or 
siibcordiform ; valves ovate, slightly oblique, a little longer than wide, 
very gibbous in the middle and toward the umbo ; beaks extended and 
incurved. Surface marked by numerous fine radiating striae.” 
In the Proceedings of the Boston Society of Natural History, Mr. 
C. A. White described Cardiomorpha patvirostris as follows: “Shell 
sub-circular in outline, slightly inequilateral; valves broadly and mod- 
erately convex; base more broadly rounded than the front and oval 
margins ; beaks small, incurved, pointing little, if any, forward. Sur- 
face marked by fine radiating lines.” 
In the meantime Meek and Worthen in Proc. Acad. Nat. Sci., 
Phila., 1 86 1, (afterwards also in volume ii of the Palaeontology of Il- 
linois) had founded the genus Cardiopsis upon a species from the same 
horizon with the following diagnosis: “Shell equivalve, somewhat 
inequilateral, very slightly oblique, ovate or cordiform, entirely closed ; 
beaks rather elevated, distinctly incurved and directed toward the an- 
terior side ; surface marked by radiating striae or costae ; cardinal mar- 
gin short and rounding into the posterior border, hinge provided with 
one or two distinct toterior teeth in each valve, near the beaks.” 
To the original species C. radiata. Prof. Winchell added three 
more in 1862, (Proc. Acad. Phila., p. 417.) C. crenistriata differs 
from C. radiata “only in its striation,” and seems to have been reunit- 
ed with that species by its author, and is omitted from the list publish- 
ed in 1870. Cardiopsis megumbonata scarcely differs and suggest that 
C. radiata may exhibit considerable variation. C. jejuna, the remain- 
ing species, seems quite distinct. 
In 1863 Prof. Winchell formed the genus Dexiobia {dexios-hid) 
to receive D. whitei (rr=C. ovatus -f C. parvirostris, which he identi- 
fied as the right and left valves respectively of the same shell) and 
another and quite different form, D. halli, which is possibly identical 
with Prof. Hairs C. rhomboidea. The diagnosis of the genus is as 
follows: “Shell thin, inequivalve, inequilateral; beaks separated by 
ail undefined area. Right valve very ventricose, with a prominent 
umbo, and a produced, incurved beak, strongly inclined forward. Left 
valve much less inflated, with a less prominent beak, scarcely elevated 
above the dorsal margin. Hinge-line more or less extended, straight, 
or slightly bent, edentulous (?) furnished with a thickened cartilage 
plate bearing a linear posterior groove. Pallial line and muscular 
marking unknown.” 
