78 
AUG. F. FOERSTE 
Bellerophon c enter villensis Sp. nov. 
Plate XIV, fig. 20 
Shell attaining a diameter of 20 mm. in a direction across the 
umbilicus; but most specimens vary between 12 and 15 mm. No 
specimen retaining the entire width of the shell at its flaring 
aperture is at hand, but from such fragments as are preserved it 
is estimated that this aperture is at least as wide as the diameter 
of the shell across its umbilicus. The general cross-section of 
the last volution is almost evenly convex, with only a faint 
tendency toward angularity toward the slit-band. The slit- 
band varies in width from about 0.4 mm. in specimens of average 
size to 0.6 mm. in a few of the larger specimens. The slit-band 
is borne on the crest of a median carina whose elevation usually 
is barely \ mm. above the general convexity of the shell, and 
never exceeds 0.5 mm. The lateral walls of this carina usually 
rise rather abruptly. The umbilicus is small, but distinct, 
varying in size between that shown by Bellerophon troosti and 
its variety hurginensisl^ Along the side of the shell, the re- 
flexed lateral margin of the posterior part of the aperture termi- 
nates against the posterior wall of the umbilicus, and there is no 
evidence of a strong posterior reflexion of the posterior or inner 
lip of the aperture along the median part of the shell It is 
possible, therefore, to see the carina and the transverse surface 
striae along that part of the last volution which usually, in species 
of Bellerophon, is covered by the reflexed inner lip of this aperture. 
The surface of the shell is covered by very fine transverse striae, 
strongly reflexed both laterally and toward the carina, very much 
as in Bellerophon recur vus Ulrich. 
Locality and formation.^ — Quarry | mile northeast of Center- 
ville, Ohio, in the argillaceous strata immediately beneath the'^ 
Brassfield limestone. 
Remarks.^ — Bellerophon centervillensis has a decidedly Ordovi- 
cian aspect. From Bellerophon consimilis Savage it differs in 
Ulrich, E. O., and Scofield, W. H., The Lower Silurian Gastropoda of Minne- 
sota; Minn. Geol. and Nat. Hist. Surv., Pal., vol. 3, 1897, pi. 64. figs. 1, 4, 6. 
Idem., pi. 64, figs. 12, 13. 
