74 PALEONTOLOGY OF NEW JERSEY. 



Genus DIONE Gray. 



DiONE Mabylandica. 



Plate xiii, fi«. 1. 



Cytheren Marylandica Oonrad: Am. Jour. Sci.,vol. 2:3, Isst ser., p. 343; Mioceue Foss., 



p. ir>, PI. IX, tig. 1. 

 J)ione Marylniidica Conrad: Proc. Acad. Nat. Sci. Phil. 1«62, p. 57.5; Meek, Check 

 List i\Iioceni> 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 

 laro-e, oblong ovate, defined by a slightly impressed line; basal margin 

 reo-ularly arcuate; cardinal teeth tlii-ee 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 remai'kably 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 delmihis, 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 Avould 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 featiu-e 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 liinge plate 

 almost as nai-row according to the thickness of the shell, and on close 

 comparison with that and other Miocene species, none show so gi-eat a 

 resemblance as B. Marylandica. So I think there is no reason t(^ doubt 

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



