22 
PROCEEDINGS OF THE ACADEMY OF 
and was implanted almost directly backward in tlie ascending border of the 
ramus, above the level of the heel of the sectorial molar. 
The portion of jaw is remarkable for its robustness ; the thickness of the 
anterior border of the ramus an inch above the ordinary line of the teeth 
being eight lines. 
The species is respectfully dedicated to Dr. F. V. Hayden, the untiring geo- 
logical explorer of the region of the Upper Missouri. 
Depth of jaw at sectorial molar, 21 lines. 
Thickness of jaw below sectorial molar, 9 " 
Extent of space occupied by the sectorial and preceding 
two premolars, 34 " 
Antero-posterior diameter of sectorial molar, 17 " 
Transverse diameter of sectorial molar, 7| " 
Space occvipied by the tubercular molars, 14 " 
Felis (Pseud^lurus) intkepidus, Leidy. 
An extinct species of the cat tribe is indicated by a well preserved specimen 
of the lower jaw of an animal intermediate in size to the Panther {Felix concolor) 
and the Lynx (Felix canadensis). The jaw together with the teeth present a 
repetition of form of the corresponding parts in known species of cats, except 
that in the middle of the hiatus behind the canine tooth there is a smaller 
socket for a rudimental premolar, as in the extinct Felis (Pseudcelurus) quadri- 
dentatus of Europe, and the sectorial molar has a basal heel and tubercle about 
half as well developed as in the preceding teeth. 
Length of the lower jaw from the condyle 58 lines. 
Height of the lower jaw at coronoid process 27 " 
Height of the lower jaw below middle molar 11 " 
Length of molar series (3) 21 " 
Antero-posterior diameter of sectorial molar 7 " 
Height at posterior cusp of sectorial molar 5^ " 
Aelurocon ferox, Leidy. 
The only specimen upon which this name is proposed, consists of an isolated, 
unworn, upper sectorial molar tooth, which has about the size and proportion- 
ate form of that of the common Wolf of this country or Europe, but has a 
tubercle or lobe in advance of the principal cusp nearly as well developed as 
that occupying the same position in the cats. 
Breadth of crown antero-posteriorly and externally 13 lines. 
Length of crown at principal cusp 8^^ " 
Thickness of crown at base anteriorly 7 " 
Thickness at base of principal cusp 5|- " 
• RODENTIA. 
HvsTRix (Hystricops) venustus, Leidy. 
Tafo isolated molar teeth, probably both referable to the same animal, have 
about the same size and nearly the same constitution as those of the Crested 
Porcupine {Hystrix cristata,) of Europe. One of the teeth appears to correspond 
with the first upper molar of the right side of the latter animal. It has a 
single deep fold on the inner side, and a less extensive one on the outer side. 
The crown, about one-fourth worn, presents on the triturating surface the fold 
extending from the inner and outer side, and in advance a bow-like enamel 
islet, and behind a transverse boot-like islet and a small circular one. The 
second specimen, viewed as an upper left tooth, has a deep fold on the inner 
side, in advance of which on the triturating surface is an oblique enamel islet, 
and behind, two similar ones. 
Antero-posterior diameter of the first molar 5|- lines. 
Transverse diameter of the first molar 4 " 
Antero-posterior diameter of the second molar 3 " 
Transverse diameter of the second molar 3|- " 
[March, 
