Mineralogy and Geology. 391 
That animals of this genus made some of the tracks similar to 
those of birds in the red sandstones of the Valley of the Connecti- 
cut there can be no doubt. It furthermore explains some prob- 
lematical impressions which are occasionally found with them. 
acks of an animal resting in a plantigrade position, as indicated 
by the moulds of two long parallel metatarsi, each terminated b 
three toes, are accompanied by a peculiar, bilobate, transversely 
oval mark on the middle line, some distance behind the heels, 
Prof. Hitchcock states that it appears to be the impression of a 
short stiff tail, The present specimen shows clearly that it was 
made by the obtuse extremities of the ischia, The saurian 
of. O. C. Marsh informs me that in the museum of Yale College, 
aslab exhibiting impressions similar to the above shows the im- 
pressions of the anterior feet also, which were put to the ground in 
orous Mammalia. 
The tracks of many of the animals discovered by Hitchcock are 
re pheumatic structure of the bones, there is abundant reason to su 
; pose that they progressed by leaps, and assumed the REE 
position when at res : 
No portion of the cranium or dentition of this genus has been 
The existence of Symphypoda in the strata here indicated, with 
e 
The remains here described were alluded to by Prof. R. Owen, 
Pterodactyles or Birds, pro- 
viding the cavities of the bones were filled by marrow, and not by 
i a 
: e 
a8 those of the Pterodactyle, I do not find that they are those of 
this animal; there is no positive pro 
: * Hitchcock, in his Technology (1858), holds that the beds containing the tracks 
_ are lower Jurassic, either rede ias; and Dana, in his Geology, (pp. 414, 443), 
Says ae agnens, a ge * 1 in p rt Jurassic.—EDs. Am. J. So : 
eae 
