74 PALEONTOLOGY OF NEW JERSEY. 
Genus DIONE Gray. 
DIONE MARYLANDICA. 
Plate x11, fig. 1. 
Cytherea Marylandica Conrad: Am. Jour. Sci., vol. 25, Ist ser., p. 343; Miocene Foss., 
[oda elk toe rites IE 
Dione Marylandica Conrad: Proc. Acad. Nat. Sei. Phil. 1862, p. 575; Meek, Check 
List Miocene Foss., p. 9. 
“Shell subtriangular, inequilateral, thick and ponderous, ventricose; 
summits prominent, obtuse, posterior side subcuneiform; posterior slope 
concave above, flattened inferiorly; posterior extremity rounded; lunule 
large, oblong ovate, defined by a slightly impressed line; basal margin 
regularly arcuate; cardinal teeth three in each valve; anterior tooth 
pyramidal and very thick.” (Conrad in Miocene Foss.) 
In the observations following the above description Mr. Conrad says 
further: “‘A remarkably thick species, but is easily broken, and always with 
the disk more or less imperfect. The anterior cardinal tooth of the right 
valve is very prominent, and somewhat fan-shaped, and slightly crested.” 
Two fragments of the hinge part of a shell accompany the fragment of 
Mactra delumbis, in the collection from the well-boring at Atlantic City, N. J., 
which have shelled one from within the other, and which when put together 
appear to represent the above species much more nearly than they do any 
other species known from the Atlantic Miocene beds. It has been a remark- 
ably thick shell and is evidently a Cytherea-like species. The posterior 
umbonal ridge is very angular and somewhat excavated on the upper side 
while the surface of the beak has been flattened or compressed, unlike that 
which would result from a Venus-like shell. The fragment has been greatly 
worn by trituration on the beach and much of the surface worn away. There 
is but one feature of it which destroys its resemblance to D. Marylandica—the 
narrowness of the hinge plate, which in that species is very wide; but so 
much wearing has taken place on this fragment, that it may well have 
belonged to that species. Still some specimens of that show a hinge plate 
almost as narrow according to the thickness of the shell, and on close 
comparison with that and other Miocene species, none show so great a 
resemblance as D. Marylandica. So 1 think there is no reason to doubt 
that it was an inhabitant of the Miocene seas of this part of the coast. 
