102 The American Geologist. Auirust, isya 
Ijroiully and imifonnl^' rounded except above where the curve 
turns rather sharply into the liingeline. Ventral margin rounded 
in front, straight and sloping upward in the posterior half to the 
acute extremity. Posterior margin short, straight, sloping for- 
ward. Cardinal margin straight except for a slight prominence 
in the region of the beaks. Anterior half of surface marked with 
closely arranged, thread-like, concentric lines. These seem to be 
wanting in the posterior half, only a few obscure growth lines be- 
ing visible here. Posterior ridge sharp and strong, very gently 
curved in its course from the beak to the produced lower angle of 
the posterior extremity of the shell. Between this ridge and a 
line drawn vertically across the shell from the beaks the surface 
is depressed, forming a widening shallow sulcus and the straight- 
ening of the ventral margin. Postero-cardinal slope concave, 
narrow, descending rather rapidl}'. Interior unknown; shell sub- 
stance very thin. 
Length 21 mm., hight 12.5 mm., greatest convexity (of a left 
valve) 2.5 mm. 
Although the internal characters are as yet unknown, the data 
obtained point very strongly toward Miller's Tcchnophorus. Com- 
pared with T. faheri Miller, the posterior end will be found to be 
longer and narrower, while there is only one posterior ridge where 
that species has two. T. extcnuatm Ulrich, another species from 
the Trenton shales of Minnesota, agrees closely in all respects ex- 
cept that it has the posterior end greatly produced. 
Form-ttion and locaUtij: In beds regarded as equivalent to the 
'.'Upper Buflf limestone" of the Wisconsin geologists and the 
Black River limestone of New York, six miles south of Cannon 
Falls, Minnesota. This horizon contains an interesting fauna, 
consisting chiefly of Lamellibranchiata, Gastropoda and Cepholo- 
poda. It follows layers filled with bifoliate Bryzoa and is suc- 
ceeded by soft shaly beds in which the predominant fossils are 
Phylloporina corticosa, Prasopora and numerous other Treposto- 
mata, and one of the so-called "branching fucoids." 
Technophorus divaricatus, n. sp. 
Plate VII, Figs. 15 and 16. 
Shell small, moderately convex, elongate, the length a little 
more than twice the hight. Beaks small, incurved, projecting 
but little above the hinge line; situated about one-third of the en- 
tire length from the anterior extremity. Dorsal margin nearly 
straight, (faintl}' concave on each side of the beaks) aliout three- 
