82 PALEONTOLOGY OF NEW JERSEY. 



Family MACTRIDiE. 

 Genus MACTRA Linnaeus. 



Mactra (Mulinia?) lateralis. 



Plate xv, figs. 1-3. 



Mactra lateralis Say: Jour. Acad. Nat. Sci. Phila., 1st ser., vol. 2, p. 309; Tuomey and 

 Holmes, Plioe. Foss. S. C, p. 97, PI. xxin, fig. 9; Emmons, Geol. of N. Carolina, 

 p. 298, fig. 226, probably by displacement of figures for 227 under the name 

 Donax; Heilprin, Proc. Acad. Nat. Sci. Phila., 1887, pp. 398, 401 and 403. 



Standella lateralis (Say's) Conrad: Proc. Acad. Nat. Sci. Phila., 1862, p. 573. 



Muliriia lateralis (Say's) Meek, Check List Miocene Foss., p. 11. 



"Shell triangular, very convex, of a smooth appearance, but with very 

 minute transverse wrinkles; lateral margins flattened, cordate, with a recti- 

 linear, sometimes concave profile, one margin rounded at the tip, the other 

 longer and less obtuse; umbo nearly central, prominent." (Say.) 



A single entire right valve and parts of hinge portion of three others 

 occur in the material from the well-boring at Atlantic City. They show a 

 much greater thickening of the shell and a proportional broader hinge-plate 

 than most of those found recent in Long Island Sound and along the coast. 

 Otherwise there is no apparent difference between these fossil shells and the 

 living form. There is some doubt as to the proper generic relations of the 

 species; but it appears to be as near Mulinia as to any described form, and 

 not distinct enough to warrant separation. 



The specimens are from the cabinet of the Academy of Natural Sciences 

 at Philadelphia. 



Mactra (Schizodesma) delumbis. 

 Plate xv, fig. 10. 



Mactra delumbis, Conrad: Foss. Shells of theTert. Form., p. 2J, PL xi, fig. 1; Miocene 

 Foss., p. 27, PI. xv, fig. 1 ; Meek, Check List Miocene Foss., p. 1L 



M. (Scissodesma) delumbis Con.: Proc. Acad. JSat. Sci. Phila., 1862, p. 572. 



Mactra ponderosa F (Conrad) Heilprin : Proc. Acad. ^at. Sci. Phila., 1887, pp. 401 and 

 403. 



" Shell subtrigonal, slightly ventricose, thin and fragile, subequilateral, 

 the beaks being rather posterior to the middle, prominent; posterior margin 

 with a distinct fold; posterior slope rather deeply depressed, narrow, the 



