74 PALEONTOLOGY OF NEW JEBSEY. 



Genus DIONE Gray. 



DlONE MARYLANDICA. 



Plate xin, fig. 1. 



Gytherea Marylandica Conrad: Am. Jour. Sci.,vol. 23, 1st ser., p. 343; Miocene Foss., 



p. 15, PI. ix, fig. 1. 

 Dione Marylandica Conrad: Proc. Acad. Nat. Sci. 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 I think there is no reason to doubt 

 that it was an inhabitant of the Miocene seas of this part of the coast. 



