NATURAL SCIENCES OF PHILADELPHIA. 



195 



On favorable report of the committees, the following papers were 

 ordered to be published : 



Notice of some remains of HORSES 

 BY JOSEPH LEIDY, M. T>. 



Mr. W. Lorenz loaned me for examination a horse tooth, black in color, and 

 devoid of its outer cementum,from diluvium, occupying a depression about six 

 feet in depth and about twenty feet in breadth, in the Silurian slate, between 

 Rutherford's Station and Highspire, Lebanon Co., Pa. It is stained in texture 

 with iron, mutilated at its lower part, and not petrified. It is a fifth upper 

 molar of an individual which had just attained maturity, and does not differ 

 characteristically from the corresponding tooth of the recent horse at the same 

 age. The inflection of enamel at the bottom of the principal internal valley of 

 the triturating surface is minute, but this is the case occasionally in the cor- 

 responding tooth in the living horse. The size of the tooth also is about that 

 of the ordinary full-sized horse. The measurements, in comparison with a 

 fifth molar contained in a recent horse skull, are as follows : 



Fossil. Recent. 



Length .. 40 lines. 34 lines. 



Breadth fore and aft 15^ " 15 " 



Width, transversely 12 " 12 " 



The tooth may be viewed as having belonged to an indigenous horse, a co- 

 temporary of the Mastodon, but it is equally improbable. 



Prof. Whitney has recently submitted to my inspection a fossil horse tooth 

 from Martinez, Contra Costa Co., California, the largest I have ever seen or 

 can recollect of being on record. The formation from which it was derived 

 Prof. Wliitney considers to be of pliocene age. The tooth is well preserved, 

 retaining its outer cementum, and is but slightly, if at all, changed in texture. 

 The tooth is a second upper molar, nearly half-worn. The triturating surface 

 in its arrangement of the enamel presents nothing strikingly different from that 

 of the corresponding tooth of the recent horse. As in this there is an inflection 

 of the enamel at the bottom of the principal internal valley, and in this respect 

 and the less simplicity of folding of the enamel islets of the triturating surface, 

 differs from Equus excdsws of the Niobrara and of California. The tooth pro- 

 bably represents an extinct species, upwards of eighteen hands high. Its 

 measurements are as follows : 

 Length along the outer median column to the origin of the fangs.... 2G.} lines. 



Breadth of triturating surface fore and aft Itij " 



Thickness independent of cementum 15 " 



" with cementum 16 " 



The species represented by the tooth may be distinguished by the name of 

 Equus pacificus. J had previously seen fragments of an upper molar and two 

 lower molars, apparently of the same species, from the same locality, submit- 

 ted to my inspection by Prof. Whitney several years ago. 



Coincidentally, Dr. Le Conte has just handed to me a bone indicating the 

 smallest species of horse of which I have any knowledge. The bone, a second 

 ungual phalanx or coronary bone, together with the proximal end of a meta- 

 carpal of a ruminant, were obtained by John C. Browne from a well 60 feet 

 deep, at Antelope, Nebraska, 450 miles west of Omaha. The coronary bone 

 in its axis is 9 lines long; the same width at the proximal end, and -rather 

 more than a line less at the distal end. From its relation of size with that 

 of the recent horse, the animal to which it belonged was about eight hands 

 high. It is uncertain to what solipedal genus the bone actually belongs, but 

 in the absence of more characteristic materials, it may be viewed as repre- 

 senting a species of Equus. 



1868.] 



