574 THE PALEONTOLOGY OF MINNESOTA. 
(Whitella precipta. 
every essential characteristic of the genus Whitella. We cannot, however, say this 
of the specimens which were referred to the species by Hall in 1859 and’ 1862, and 
Whithfield in 1882, since in these cases we are dealing with inequivocal types of 
Cyrtodonta. The interior figured by Hall in vol. iii, Pal. N. Y.,as Palewarca ventricosa, 
is very different from the original Hdmondia (now Whitella) ventricosa. That shell 
seems to belong to the species previously described by Billings as Cyrtodonta sub- 
carinata. The cast figured by Whitfield, if correctly represented, belongs to a species 
of Cyrtodonta as yet unknown to me. In his description, however, he included the 
species which I have named and described on page 587 as Cyrtodonta janesvillensis. 
Comparing W. ventricosa with other species of the genus, W. subcarinata will be 
found to have a sharper and more prominent umbonal ridge. In W. rugatina and 
W. concentrica the anterior end is much larger; W. precipta is much narrower poste- 
riorly and a more elongate shell. 
Formation and locality.—In New York the species occurs in the Trenton limestone at Watertown, 
Middleville and other localities. If it really occurs in Minnesota, it will be, I think, in the middle 
Galena-of Goodhue and Fillmore counties. B 
WaHiteLta pRaHcrptTa Ulrich. 
PLATE XLI, FIGS. 15 and 16. 
Whitella precipta ULRICH, 1890. Amer. Geol,, vol. vi, p. 386; more fully described and figured in 
1892, Nineteenth Ann. Rep. Geol. and Nat. Hist. Sur. Minn., p. 246. 
Shell of medium size, ventricose, very oblique, elongate-ovate or subrhomboidal 
in aside view, produced and sharply rounded in the postero-basal region. Beaks of 
moderate size, prominent, strongly incurved; umbones full; umbonal ridge well 
marked, traceable almost to the posterior extremity. Anterior end small, short, 
narrowly rounded; ventral margin gently convex; posterior end produced and 
narrowly rounded in the lower part; from the point of greatest extension to the 
posterior side of the projecting umbones the outline is gently and almost uniformly 
convex. Hinge line comparatively short, its length less than half the length of the 
shell, the edge inflected to form a distinct escutcheon, extending somewhat in front 
of the beaks. In casts of the interior the internal ligament supports have left 
distinct impressions of unusual width on each side and behind the impression pro- 
duced by the escutcheon. An obscurely defined ridge and sulcus is also to be seen 
running through the middle of the cardinal slope. Anterior muscular scar faint, 
subovate, acuminate below, situated very near the anterior extremity. Pallial line 
represented by a thin raised line running parallel with the margin of the cast. 
This species is very similar to W. obliquata Ulrich, from the upper beds of the 
Cincinnati group, yet I do not doubt that they are really quite distinct species. 
That species grows to a larger size, is less elongate, wider posteriorly and with the 
