31 
has besides three leptodactylous toes pointing for- 
wards, a fourth extending backwards in a remarkable 
way, like the handle of a trident; the impression, 
however, being expanded so as to show an extensive 
displacement of the mud. All the specimens of 
Trizenopus are in a beautiful red shale, very thin and 
fragile, but presenting well-defined impressions, gen- 
erally about three inches long. 
There are two species to this genus. Of the 
Trr=nopus EmmonstANus we notice three impressions 
in relief. In another specimen there is the appearance 
of a part of the toes of the Anomcepus Scambus, and 
on the upper side are seen two excavations correspond- 
ing with the three impressions. In the last slab, the 
track of the Tr1#norus BatLeyaNnus appears to have 
been made by two feet placed successively in the same 
spot, which led President Hitchcock to suspect it 
might have been made by a quadruped. One of the 
specimens has the Triznopus tracks intermixed in a 
peculiar way with other impressions. 
The specimen representing the genus HaArpepac- 
TYLus is larger than the preceding; and, though 
leptodactylous, the toes are much broader and also 
more curved, whence the name Harpedactylus, sickle- 
finger, from éprn and daxrvioc. 
