560 THE PALEONTOLOGY OF MINNESOTA. 
« 
[Vanuxemia abrupta. 
ridge, and longer hinge line. Of associated species, Crytodonta glabella Ulrich, has a 
similar outline, but there is no relationship between them since that species is as 
true a Crytodonta as this is a Vanuxemia. 
Formation and Locality.—In the upper part of the middle third of the Trenton shales, Goodhue 
county and Chatfield, Minnesota. 
VANUXEMIA ABRUPTA 2. Sp. 
PLATE XXXVIII, FIG. 39—44. 
» Shell a little beneath the medium size for the genus averaging 20 mm. high and 
24 mm. long; rounded or subquadrate in outline, with subterminal beaks, tumid in the 
umbonal region and in front of the center, the anterior end very obtuse, the surface 
in the upper part rounding abruptly inward to the edges of the valves so that in a 
side view of casts of the interior the sharply defined anterior muscular scar is quite 
hidden beneath the filling of the umbones. Hinge line straight, long, terminating 
more or less abruptly posteriorly; posterior margin broadly rounded, occasionally 
nearly erect, usually a little oblique; anterior side truncated above, rounding below; 
base rounded. Casts have full and rounded and well incurved beaks, and the con- 
vexity of the surface continues without a sign of the sulcus and ridge exhibited by 
the casts of so many species of this genus. As near as can be determined from the 
impré&sions, the hinge plate was narrow and bore two, in one case apparently three 
slender posterior lateral teeth and two cardinal teeth in each valve. Pallial line and 
posterior muscular impression very obscure. Surface almost smooth, the best 
specimens only showing remains of fine concentric lines. 
This well marked species is believed to be related to V. nana and V. hayniana, 
but the subterminal beaks and obtuse anterior end will distinguish it at once. From 
V. terminalis of the lower Trenton, which certainly is also very much like it and 
perhaps a more natural ally, it is separated by the more erect form. 
Formation and locality.—Middle Galena, Fillmore and Goodhue counties, Minnesota. 
Vanuxemia niota Whitfield (?Hall). 
PLATE XXXVIII, FIG. 35. 
?Cypricardites niota HALL, 1861, Rep. Supt. Geol. Sur., Wis., p. 20; also 1862, Geol. Rep., Wis., vol. i, 
p. 38, Fig. 8, p. 438. 
Cypricardites niota WHITFIELD, 1882, Geol. Rep., Wis., vol. iv, p. 208. 
Iam very much inclined to doubt that this species, a specimen of which was 
submitted to Prof. Whitfield, is the same as the one described by Prof. Hall. If it is, 
then the original description is anything but accurate.* 
* Hall’s original description of Crypricardites niota reads as follows: “Shell broadly subovate, broadest at the posterior 
end; umbones very gobbous, beaks incurved, little elevated, situated about one-fourth of the length of the shell from 
the anterior end. Oardinal line straight or little curved; anterior, posterior and basal margins rounded. Anterior muscular ~ 
impression situated near the cardinal line, well defined; posterior imprint obscure. Surface of the shell marked by con- 
centric lines of growth. This species differs from O. rotundata in being more oblique, in the straighter cardinal line, and less 
ventricose form. It is intermediate between that species and C. ventrecosa, from which it difiers in less obliquity and the 
greater length from beak to base.” ‘Length, one inch and a quarter; hight, one inch.” 
