32 PALEONTOLOGY OF NEW JERSEY. 
species, as several of them have ribs distinctly alternating in size and quite 
unequal, with probable implantations or -bifurcations, while others have 
ribs of an even size and simple. I do not think they could well have 
been opposite valves of the one species. The specimens are too poor and 
meager to illustrate, but I do not think they represent P. vicenarius as above 
described, and as the species has never been figured, there is nothing but 
the description to guide one in determining it. The types were from Wil- 
mington, N. C. I do not recognize these fragments as pertaining to any 
described form, unless possibly the simple ribbed form might represent 
P.micropleura of H. C. Lea,* though some of them have not had a sufficient 
number of ribs. Or they may be related to P. tricenarius of Conrad,* but 
they are too imperfect for determination. 
Genus VOLA Klein. 
VoLA HUMPHREYSI. 
Pl. Iv, figs. 6-9. 
Pecten Humphreysvi Conrad: Proc, Nat. Institute (2d Bulletin), p. 194, Pl. 11, fig. 2; 
Cat. Miocene Foss., Proc. Acad. Nat Sci. Phil., Dec. 1862, p. 582; Meek, Check 
List Smith. Inst., p. 4; Heilprin, Mioc. Moll. State of New Jersey, Proc. A. N.S. 
Phil., 1887, p. 297 et seq.; Heilprin, Cont. Tert. Geol. & Pal. U.S., p. 8. 
Vola Humphreysti Conrad: Cat. Mioc. Foss, Proc. A. N. 8. Phil., 1862, p. 582. 
Mr. Conrad’s description of this species is as follows: ‘‘Suborbicular, 
inferior valve convex; superior flat, and with about seven remote, narrow, 
convex ribs, and concentrically wrinkled; towards the apex is a concave 
depression; ears equal, sides direct and straight; inferior valve with the ribs 
wide, approximate, plano-convex and longitudinally striated; one of the 
sars emarginate at the base.” In his observations he states that, ‘‘Of two 
specimens in the collection of the college at Annapolis, the largest measures 
3 inches from beak to base.” 
Prof. Angelo Heilprin in a recent paper® proposes the varietal name 
Woolmani tor the New Jersey specimens of the species, considering them 
‘Trans. Am. Phil. Soc. Penn., vol. 9, p. 19; pl. 35, fig. 32. 
? Miocene Foss., p. 74; Pl. 42, fig. 2. 
°’Proc. Acad, Nat. Sci. Phil., 1887, p. 405. 
