554 THE PALEONTOLOGY OF MINNESOTA. 
[Vanuxemia obtusifrons. 
thickening of its shell in the umbonal and anterior parts. The beak is compressed 
in the cast, very prominent and not at all meurved; the anterior muscular scar 
strongly defined, large, of subcircular form with the inner side truncated; the pallial 
line is distinguishable all around and, for some distance beneath the anterior muscle, 
strongly defined by a deep and unusually wide furrow, out of which the anterior 
side of the body of the cast rises very abruptly.. Ligamental area high and strongly 
striated longitudinally; cardinal teeth strong, comparatively Jong and _ slightly 
curved, three in number; posterior lateral teeth three, strong and a trifle more 
oblique than the cardinal teeth. Dorsum of cast broad and flat. - 
The external characters of the shell are unknown, but as the species doubtless 
belougs to the most typical section of the genus, they will probably prove much as 
in V. inconstans, V. dixonensis and V. rotundata. 
Formation and locality.—Middle third of the Trenton shales, St. Paul, Minnesota. 
VANUXEMIA OBTUSIFRONS Ulrich. © 
PLATE XXXVIII, FIGS. 15-19. 
Cypricardites obtusifrons Uxricu, March 3, 1892. Nineteenth Ann. Rep., Geol. and Nat. Hist. Sur. 
Cypricardites vicinus eat: Shae ee Bull. Minn. Acad. Nat. Sci., vol. iii, p. 339. 
Shell rather large, moderately ventricose, very oblique, subovate, much the 
highest and broadly rounded posteriorly, with the beaks subterminal, incurved, not 
very prominent nor large, and the umbones strongly rounded. Anterior end obtuse, 
the upper part forming nearly a right angle with the hinge line, the slightly project- 
ing junction between the two lines rather sharply rounded; postero-basal half of shell 
broadly semielliptical; dorsal outline very gently concave. Surface markings con- 
sisting of irregular, fine and coarse, sublamellose lines of growth. 
Casts of the interior with the beaks large, very prominent, compressed and 
strongly incurved at their apices; umbonal ridge and sulcus of moderate definition, 
nearly parallel with the anterior margin. Anterior muscular scar large and strongly 
defined, excavated out of the hinge plate, in the cast having the appearance of a strong 
process projecting from the under side of the base of the beak forward and upward 
to the anterior extremity of the hinge; posterior scar illy defined, large, ovate, situ- 
ated close to the posterior end of the hinge. Pallial line distinct. 
Hinge with three cardinal and three posterior lateral teeth in each valve, both 
sets strong. The cardinal teeth are situated under the beaks, finely toothed on 
their sides, slightly curved and usually oblique, ranging at an angle of 45° or more 
with the hinge line.* 
*The original figure of the interior of this species is faulty in its representation of the cardinal teeth. The type 
specimen has been injured at this point and in such a manner that I quite overlooked the actual remains of the teeth 
