ORDOVICIAN FAUNAS. aly) 
rather than with the Gasteropods, his type species cannot be mistaken. 
Under these conditions, the name Phragmolites is used in this place 
rather than Conradella. 
OXYDISCcUS suBACUTUS Ulrich. 
Plate XII., Figs. 8-9. 
1897) Oxydiscus subacutus Ulrich, Pal. Minn., pt. IL., p. 913, pl 
62, figs. 62-65, pl. 82, figs. 23-25. 
Description.—‘Shell lenticular; dorsum acutely carinated; greatest 
diameter from 15 mm. to 28 mm.; greatest thickness or width nearly 
one-half the diameter. Volutions three and one-half to four and one- 
half, thickest near the umbilicus, from which the surface ascends, first, 
with a gently convex, then with a concave slope to the sharp periphery ; 
each volution embracing between one-third and one-half of the pre- 
ceding one; umbilicus exposing all the whorls; its width somewhat 
less than one-third of the diameter of the shell; edge of umbilicus 
abrupt, subangular; aperture obcordate, indented below by the sharp 
dorsum of the perceding whorl; margin of aperture thin, in a side 
view with a strong, backward sweep; slit long, very narrow. Surface 
marked by fine and rather indistinct lines of growth.”—Ulrich. 
PTEROTHECA EXPANSA (Hmm.) ? 
Plate XII., Fig. 35. 
1842. Delthyris expansus Kmmons, Geol. Rep. 2d Dist. N. Y., p. 
397, figs. 109-112. 
1861. Choderma expansa Hall, 14th Ann. Rep. N. Y. State Cab. 
Nat eElist:: p98: 
A single imperfect specimen, which may belong to this species, has 
been observed. It is a shell which, when complete, was subellipti- 
eal in outline and strongly carinate along its median line. Each 
lateral slope from the median line of the shell is at first abrupt to 
