88 [April, 



Notices of Remains of Extinct Mam-naUa, discovered hy Dr. F. V. Hayden, in 



Nebraska Territory. 



Bj Joseph Leidy, M D. 



PACHYDERMATA. 



1. Leptochokrus spectabilis, Leidy. 



The genus and species are proposed upon a small frag:ment of the lower jaw 

 of an apparent suilHne animal, containing two molar teeth, which appear to be 

 the first and second true molars. The crowns of these teeth have the general 

 form of the correspondi^.g ones of the Peccary, and they are composed of four 

 tubercles or lobes confluent into a thick base, with a ridge anteriorly and pos- 

 teriorly, and between the outer lobes externally. Of the four lobes that postero- 

 internal is the largest, the external pair are nearly equal, and the antero-internal 

 one is smallest. The inner lobes are trilateral, and the outer ones are much like 

 the corresponding lobes of ruminants. The aims of the crescentoid summits of 

 the outer lobes join the inner lobes ; that most anteriorly joining the antero-iii- 

 ternal lobe, while the other three join the postero-internal lobe. 



Antero- posterior diameter of first true molar 2i lines. 



Transverse, do. do. do. 2 " 



Antero-posterior, do. second do. 3 " 



Transverse, do. do. do. 2j " 



Discovered in the Mauvaises Terres of Nebraska. 



RUMINANTIA. 



2. Leptaochbnia decora, Leidy. 



In Dr. Hayden's collection there are several specimens from the valley of 

 White River, Nebraska, consisting of fragments of upper and lower jaws with 

 teeth, which belonged to a ruminating animal allied to the Camel. 



One of the fragments contains the left superior true molars and the last pre- 

 molar. The true molars have their crowns more nearly square than in either 

 the Camel or Lama, and the anterior folds of their outer lobes are produced rela- 

 tively much more outwardly and forwards than in either of the latter. The 

 surfaces between the folds are concave and directed much more obliquely back- 

 ward than in the Camel. The last premolar is bilobed and holds the same relation 

 of position of its outer face to the true molars as in the Camel. 



In several fragments of lower jaws containing the last two true molars, and 

 in another with the anterior two true molars, these teeth have a strong resem- 

 blance to the corrt-sponding teeth of the Camel. 



Another fragment of a lower jiw discovered by Dr. Hayden, on Bear Creek, 

 Nebraska, appears to belong to the same animal as the former, though this may 

 not be the fact. It contains the alveoli for three incisors, a canine, and three 

 premolars. The incisive alveoli are in close relationship as in the Lama. Tne 

 canine is separated from the former by a hiatus of less than one line, and it has 

 nearly the form of the corresponding tooth in the Camel. Posterior to the 

 canine and separated from it by a hiatus of less than two lines, there is a portion 

 of the first premolar, which appears to have had nearly the same form as the 

 canine. The succeeding two premolars are separated from the first by a hiatus 

 of a little more than four lines. These are inserted by two fangs, are in close 

 contiguity, and have broad, laterally compressed, pyramidal crowns, bearing 

 considerable resemblance to the premolars of the Musks. 



Length of series of upper true molars and last premolar 

 Antero-posterior diameter of second true molar 

 Transverse do. do. 



Length of series of lower true molars 

 Antero-posterior diameter of last true molar . 

 Depth of lower jaw below do. 



Depth of lower jaw below second premolar . 

 Breadth of crown of third premolar 

 Breadth of crown of second premolar 



