10 
PROCEEDINGS OP THE ACADEMY OP 
of a yellowish magaesian limestone containing numerous casts of a very peculiar 
group of fossils. On examining these, it was soon observed that they are quite 
unlike any forms known to us in the carboniferous system, and very nearly allied 
to types considered characteristic of the Permian, of the old world. Major Hawn 
was at once apprised of this fact, and he has since informed us of several facts 
in relation to this formation, which rather go to confirm the view that it may 
prove to be of Permian age, rather than otherwise. In the first place, he informs 
us that the bed from which the fossils were obtained, hold a position, above the 
well marked coal measures, and seems to have been deposited upon an uneven 
surface, as though the coal measures had been worn into hills and valleys previous 
to the deposition of the rock of which we speak." [Signed, Meek and Hayden.] 
Dr. Leidy directed the attention of the members to some fossils on the table, 
being part of the collection obtained by Dr. F. V. Hayden, in the valley of the 
Niobrara river, Nebraska. One of the specimens was the lower jaw of a new 
species of Mastodon. It belonged to an old individual, as the last molar tooth 
occupies its functional position and is considerably worn. The jaw indicates a 
smaller animal than the common Mastodon (J/. Ohioiicus.) The tooth resembles 
the corresponding one of M. sivalensis, or of 31. anffusiidens, much more nearly 
than that of the common Mastodon. The crown has a much greater antero- 
posterior diameter in relation to its transverse diameter, than in the latter, and 
it has six transverse rows of tubercles, together with a feeble tarsus. The tuber- 
cles are crowded instead of being separated by wide angular valleys as in the 
common Mastodon. The tooth was compared with that from an unknown 
locality, characterized by Dr. Hays under the name of 31. Chapmani; but this 
more nearly resembles the South American species M. Hurnboldti. In advance 
of the tooth, there are no traces of an alveolus for the preceding tooth, but a 
sharp ridge proceeds from the last molar to the anterior extremity of the jaw. 
Dr. Leidy observed he had never seen the jaw of the common Mastodon in the 
same condition, as the oldest individuals always presented the fifth alveolus 
filled up, and not completely obliterated. The species he named llastodon min- 
ficiLS. 
Dr. Leidy next exhibited part of an upper molar tooth of an Elephant from 
the Niobrara ; which he suspected to be a species distinct from those previously 
indicated, though it does not present sufficient characters to establish the opin- 
ion. It is the broadest tooth he had ever seen, being almost five inches, and it 
has fewer plates of enamel than in any variety of teeth of Elcphas Americanus 
that had come under his inspection. The species he proposed to distinguish by 
the name Elephas imperator. 
Dr. Hays called attention to the fact that the tooth of the new Mastodon had 
protruded more obliquely forward and upward than in the common species, indi- 
cating a nearer alliance to the Elephant. 
Dr. Leidy thought Dr. Hays quite correct, and that the last molar in protruding 
forward and upward had gradually displaced two preceding teeth, whose posi- 
tion it now occupied. He then described the mode of development and succes- 
sion of the teeth in the Elephant ; and he showed, as observed by Dr. Hays in 
the new Mastodon, that we have a closer approximation to the same process, 
than in the common species. 
On leave granted. Dr. Oamac offered the following special resolution : 
Resolved^ That a committee of three be appointed to obtain and stock a ma-, 
rine aquarium to be placed in the Hall of the Academy, provided that the 
necessary amount be raised by subscription — which was adopted, and the com- 
mittee appointed to consist ©f Drs. Camac and Rand, and Mr. J. D. Sergeant. 
[March 
