180 PALEOZOIC PALEONTOLOGY. 
the base of the carina and is then gently convex to the lateral mar- 
gins, with a single, shallow, rounded furrow extending from the apex 
obliquely to the postero-lateral margin. 
The approximate dimensions of the shell must have been: length, 
24 mm.; width, 30 mm. 
RAPHISTOMA PERACUTUM U. & S. 
Plate XII., Figs. 22-28. 
189%. Raphistoma peracutum U. & 8., Pal. Minn., pt. IT., p. 940, pl. 
68, figs. 1-6. 
Description.—‘Shell small, not known to exceed 12 mm. in di- 
ameter, consisting of three or three and one-half whorls, flat above, 
rounded below; periphery very sharp and thin; umbilicus equaling 
a little more than a fourth of the greatest diameter, its edge nar- 
rowly rounded; height of shell very slightly exceeding a fourth of 
the width. Surface marked on the flat, upper side with very fine, 
subequal striz, sweeping on the whole rather strongly backward from 
the suture. About a third of the width of a whorl from the suture 
the strie are interrupted by a delicate, revolving line. Between the 
latter and the extreme edge of the peripheral carina the striz make 
a distinct, sigmoid curve. Below the periphery the surface is marked 
with similar strie, which, in descending, curve first forward and then 
almost directly toward the centre of the umbilicus.”—Ulrich and 
Scofield. 
Remarks.—The specimens of this species in New Jersey are all 
poorly preserved, but seem to agree essentially with the Minnesota 
species, whose description has been copied above. They also essen- 
tially agree with the western specimens in their geological horizon, 
as they have only been observed in New Jersey in the lower or Black 
River horizon of the formation associated with Leperditia fabulites 
and Dalmanella subequata. In none of them are the delicate surface 
markings well preserved, but upon one specimen the revolving line 
about one-third of the width of the whorl from the suture can be 
detected. The New Jersey specimens sometimes attain a diameter of 
15 mm., which is a little greater than the dimensions mentioned in 
the original description. 
