614 THE PALEONTOLOGY OF MINNESOTA. 



[Technophorus extenuatus. 



TECHNOPHORUS EXTENUATUS Ulrich. 



PLATE XXXVII, FIG. 34; PAGE 611, FIG. 45-. 



Ttchnophorus? 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 concave 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 punctae. 



Length about 21 mm., greatest bight 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. 

 Technophoru* subacutus ULKICH, 1892. Amer. Geol., vol. x, p. 101. 



Shell small, rather ventricose, 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 posterior straight and sloping back- 

 ward slightly to the acuminate extremity of the hinge line. In a 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, 



