MIOCENE MOLLUSCA AND CRUSTACEA. 6 
ce | 
SINUPALLIA. 
Family VENERID 4. 
Genus VENUS Linneus. 
VENUS DUCATELI. 
Plate x1, figs. 1-7. 
Venus Ducateli, Conrad: Miocene Foss., p. 5, Pl. Iv, fig. 2; Proc. Acad. Nat. Sci., 
1862, p. 574; Meek Check List, p. 9; Heilprin, Tert. Geol. U. S., p. 8; Acad. 
Nat. Sci., Phil., 1887, pp. 397 and 403. 
“Shell suborbicular, convex, thick; disk with numerous approximate, 
recurved ribs, laminar and much elevated towards the posterior margin; 
extremity obtuse; beaks distant from the anterior margin; umbo not inflated; 
lunule defined by an impressed line, not very profound; posterior margin 
rectilinear; two of the cardinal teeth in the left valve remote, thick, bifid; 
anterior tooth much compressed.” —(Conrad.) 
Mr. Conrad’s type specimens, a very imperfect right valve and two 
fragments, are before me. I have also seve ‘al other valves, and one pair 
of valves, which appear to me to belong to the same species, but they 
differ mostly in the outline form and in the character of the surface. 
This latter feature, however, is one on which no reliance can be placed, 
as the true surface characters have been denuded or removed by the 
action of weather or by corrosion. The surface in their present condition 
is very rugose, being marked by heavy elevated ridges which are left 
standing separate, by the removal of the adjoining ribs, or of intermediate 
portions of the outer layers of the shell; still they do not show evidences 
of having ever possessed the structure now seen on Mr Conrad’s speci- 
mens. Yet I have no doubt they originally possessed it to a greater or 
less extent. They present very close resemblances to Venus mercenaria 
in many respects, but are thicker on the margin, rather more ventricose, 
shorter posteriorly, and lack the slight flattening between the middle of 
the valves and the posterior umbonal ridge which so generally marks 
specimens of that species. In the interior the anterior cardinal tooth of 
the left valve is generally bifid as well as the other, which in V. mercenaria 
is not the case, and the posterior tooth is placed at a different angle, being 
