612 THE PALEONTOLOGY OF MINNESOTA. 
(Technophorus. 
anteriorly, situated in the cavity of the umbonal ridge about midway between the 
beaks and the posterior extremity of the shell; posterior pedal muscles strongly 
defined, situated on each side of the cardinal edge and just behind the hinge plate. 
Pallial line distinct, especially in front.and along the base, sinuate posteriorly. 
This fine shell is in no wise related to Clidophorus, to which genus I originally re- 
ferred the indifferently preserved casts upon which the species was founded. Had I 
been acquainted with the appearance of casts of the interior of Lyrodesma, which are 
really very distinctive, it is not likely that I should have been led astray by the slit- 
like vertical depression in front of the beaks. Compared with other species of the 
genus, L. major is unusually long posteriorly and narrow without running to an 
acuminate extremity, the radiating lines on the umbonal ridge are finer and the 
muscular scars deeper. The species is so distinct that detailed comparisons are 
scarcely necessary. Still it may be well to say that L. acwminatum and L. cannonense 
are pointed instead of rounded posteriorly and have much stronger umbonal ridges, 
while they are also less convex in their basal outlines. 
Formation and locality.—A small valve apparently belonging to this species was found in the Hudson 
River group near Spring Valley, Minnesota. Casts of the interior are not uncommon near the tops of the 
hills about Cincinnati,Ohio. These are proportionally alittle longer than the geologically higher form of 
the species which is represented in my cabinet by excellently preserved testiferous examples from the 
upper beds of the Cincinnati group at Clarksville, Ohio. 
Family TECHNOPHORIDA, Miller. 
Genus TECHNOPHORUS, Miller. 
Technophorus, MILLER, 1889. North Amer. Geol. and Pal., p. 514. 
Shell small, equivalve, inequilateral, compressed convex, often attenuate and 
extended posteriorly; anterior end rather short, wider than the posterior, almost reg- 
ularly rounded in outline; beaks very small, scarcely, if at all prominent; one or two 
sharp ridges, with a furrow above each, arise near the beak and extend in a curved 
direction to the post-basal margin. Anterior part of surface marked with regular 
concentric lines, generally separated by rows of minute puncte; on the posterior 
part, especially the cardinal slope, those lines rarely coincide with the margins of 
the valves, but assume various arbitrary and sometimes ornamental arrangements. 
Internally a short and thick rib extends downward in each valve from the hinge 
directly in front of the beaks, while on the posterior side of same a shorter oblique 
rib, or a mere thickening of the hinge plate, causes the beaks in casts of the interior 
to appear much more erect and prominent than they do on the exterior of the shell. 
In casts the beaks of the two valves are not distinguishable but together form a single 
pyramidal prominence. Anterior adductor scar small, situated immediately in front 
of the internal rib; posterior scar and pallial line not observed, although most 
excellent casts were studied. 
