82 PALEONTOLOGY OF NEW JERSEY. 
Family MACTRIDZ. 
Genus MACTRA Linnus. 
MACTRA (MULINIA?) LATERALIS. 
Plate xv, figs. 1-3. 
Mactra lateralis Say: Jour. Acad. Nat. Sci. Phila., Ist ser., vol. 2, p. 309; Tuomey and 
Holmes, Plioe. Foss. 8. C., p. 97, Pl. xx1u1, fig. 9; Emmons, Geol. of N. Carolina, 
p. 298, fig. 226, probably by displacement of figures for 227 under the name 
Donux; Heilprin, Proc. Acad. Nat. Sci. Phila., 1887, pp. 398, 401 and 403, 
Standellu lateralis (Say’s) Conrad: Proe. Acad. Nat. Sci. Phila., 1862, p. 573. 
Mulinia 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; wnbo 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 the Tert. Form., p. 20, Pl. x1, fig. 1; Miocene 
Foss., p. 27, Pl. xv, fig. 1; Meek, Check List Miocene Foss., p. 11. 
M. (Scissodesma) delumbis Con.: Proc. Acad. Nat. Sci. Phila., 1862, p. 57 
Mactra ponderosa ? (Conrad) Heilprin: Proc. Acad. Nat. Sei. Phila., 188 
403. 
» 
ae 
q 
‘ 
, pp. 401 and 
“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 
