392 ; [Aveust, 
leneth. The eyes are rather small. The dorsal fin is longer than high; its 
-anterlor margin situated almost at the same distance from the snout and the base 
of the caudal fin. Caudal fin forked. Anal back of the dorsal. Base of ven- 
trals behind the anterior margin of the dorsal; tip not reaching the anal fin. 
Pectorals not reaching the base of ventrals. The pectorals, ventrals and anal 
are proportionally small compared to the dorsal. 
D9.A8.C 3.f8. 8.13. V8. P 14. 
Scales large; lateral line running through the middle of the sides, slightly - 
bent downwards on the abdomen. 
Back brownish yellow; a greenish grey stripe down each side covering the 
lateral line. 
Caught in Otter creek, Arkansas. 
On leave granted, Dr. Leidy made the following communication : 
Dr. John Evans, who is now engaged under the United States government to 
survey part of Oregon, recently sent to the Academy for examination, ten boxes, 
containing alarge quantity of mammalian and chelonian fossils,from the Mauvaises 
Terres of Nebraska. In this large collection, it is worthy of remark, there is 
not to be found a single fragment of a bird or a fish bone. Most of the animals 
indicated by the remains, have already been described in Dr. D. D. Owen’s 
Geological Report, and in the ** Ancient Fauna of Nebraska” of the author. The 
collection contains several new genera and species of mammalia, besides frag- 
ments of important parts not before obtained of those species described. 
A very large proportion of the collection consists of remains of Oreodon, of 
which there are fragments of about two hundred individuals. The species O. 
Culbertson, predominates, and then follows O. gracilis ; ; while of O. major 
there are very few fragments. This enormous quantity of remains of Oreodon, 
would indicate that the animal was gregarious, and existed in immense herds like 
the recent Peccary or Bison. 
Only a few small fragments of Poebrotherium Wilsonit and Agriochoerus 
anttquus are contained in “the collection. 
Of the two species of Rhinoceros, R. occidentalis and R. Ni ebrascensis, there 
are remains of numerous individuals. 
Of Entelodon Mortonz the collection contains portions of several crania. 
Of Anchitherium Bardi there are four crania and numerous small fragments 
of others. 
Of the huge Tvtanothertum Proutit there are numerous small fragments of 
bones and teeth; and also several entire superior molars, which have served 
to remove some of the obscurity in regard to the characters of the animal. From 
the last mentioned specimens it appears that those, which have been described 
as probably indicating a new species of Palzotherium, under the name P. gigan- 
tewm, (Ancient Fauna of Nebraska, pl. XVII, figs. 11-13,) belong to Lvtanothe- 
rium Proutit, while several superisr molars (Ib. figs. 1-7), attributed to the latter, 
belong to a new genus associating characters of Rhinoceros and Paleotherium. 
For this genus and species, represented by figures 1-7, plate XVII, in the Ancient 
Fauna of Nebraska, I propose the name of KFotaertum AMERICANUM. 
Of Machatrodus primaevus there are preserved several crania and some other 
bones. 
Of the new mammalia above referred to, there are four carnivora and one rumi- 
nant. The carnivora consist of three species of Hyenodon and a new genus. 
The ruminant is a new genus closely allied to the recent Moschus. These 
interesting animals I propose to name as follows: 
1. Hy znopon HORRIDUS, Leidy.—This is the largest of the three spe cies above 
seferred to. It is founded upon a much fractnred skull and lower jaw; but on 
both sides of the specimen the teeth are preserved nearly perfect. The formula 
of the dentition is as follows: 
3 1 7 
in. — ¢. — mol, — 
3 1 7 
