614 THE PALEONTOLOGY OF MINNESOTA. 
(Technophorus extenuatus. 
TECHNOPHORUS EXTENUATUS Ulrich. 
PLATE XXXVII, FIG. 34; PAGE 611, FIG. 45—i. 
Technophorus? extenuatus ULRICH, 1892. Nineteenth Ann. Rep. Geol. and Nat. Hist. Sur. Minn., p. 222. 
Casts of the interior small, compressed, somewhat elongate, alated and drawn 
out posteriorly. Beaks small, erect, moderately prominent, together forming a low 
pyramidal prominence, situated about one-fourth of the entire length from the ante- 
rior extremity. Just in front of the beaks the casts of the interior exhibit a deep 
though not very long impression; the posterior umbonal rib left an obscure furrow 
on each side of the hinge line. Anterior end broad, rounded, most prominent in the 
upper third; ventral margin broadly convex and slightly produced a little in front 
of the middle; behind this point the outline is nearly straight (slightly concave) 
sloping up toward the narrow (? pointed) posterior extremity. Cardinal line nearly 
as long as the entire shell, gently concaye behind the beaks. A thin sharply defined 
ridge, slightly curved, extends across each valve from the beak to the lower side 
of the posterior end. Surface gently convex in the anterior half, faintly constricted 
in front of the ridge, and marked with obscure, concentric wrinkles of growth. A 
specimen preserving a small part of the shell, shows that the external surface is 
marked, at any rate on the sides, by closely arranged, sharp, elevated lines, separated 
by rows of small puncte. 
Length about 21 mm., greatest hight 10 mm., greatest convexity about 3.5 mm. 
This species, which I now regard as undoubtedly congeneric with the Cincinnati 
shell upon which Dr. Miller founded the genus Technophorus, is distinguished by the 
prominently rounded centro-basal margin, and the greatly produced posterior wing. 
Formation and locality.—Middle third of the Trenton shales, Minneapolis and St. Paul, Minnesota. 
TEcHNOPHORUS suBAcuTUS Ulrich. 
PLATE XL, FIGS. 33 and 34. 
Technophorus subacutus ULRICH, 1892. Amer. Geol., vol. x, p. 191. 
Shell small, rather ventrizose, alated posteriorly, the hight and length respec- 
tively as two is to three. Cardinal margin nearly straight, anterior end uniformly 
rounded, ventral edge more gently curved, the posterier straight and sloping back- 
ward slightly to the acuminate extremity of the hinge line. Ina cast of the interior 
of a left valve, the small beak is erect, projects prominently above the hinge line, 
and is situated about one-third of the entire length from the anterior extremity. 
Just in front of the beak there is a strong and deep impression, running almost 
vertically downward. On the anterior side this slit margins a rather large muscular 
scar. Extending backward from the beak the cast exhibits another, but in this case, 
