Cope.] 4bb [Nov. 15, 



with part of a lower jaw with symphysis, la the museum of the Wagner 

 Free Insthute of Science, of Philadelphia. 



Leidy remarks of this species that it is not possible to distinguish it from 

 the E. caballus by the teeth, and he has not oflFered any other characters 

 by which to distinguish it. I was therefore compelled to omit mention of 

 it from my table of the American species of Equus, published in the 

 Proceeds. American, Philos. Society, 1884, p. 10, and Annual Report of the 

 Geological Survey of Texas for 1892, "Vertebrate Paleontology," p. 66. 

 Subsequently I had the oppjrtunily of examining the dentition and mandi- 

 ble of a horse from Florida, determined by Leidy as the E. fraternus and 

 preserved in the museum of the Wagner Free Institute of Science of 

 Philadelphia. One set of dentition belonged to a young horse and the 

 other to an adult. In both the posterior wall of the cup of the incisor 

 teeth is extensively interrupted, so as to reduce the triturating surface to 

 a single crescent. Ou account of this character I proposed to refer the 

 species to a distinct genus, which I called Tomolabis, regarding it as a 

 degenerate offshoot of the genus Equus. A reexamination of the speci- 

 mens together with the observations above recorded on the incisors of the 

 E. intermedius, suggests that an examination of a larger amount of mate- 

 rial will be desirable before the validity of this genus can be established, 

 since it is possible that a full series of gradations between the characters 

 of the incisors in E. fraternus and E. intermedius may be established. 



It is demonstrated by the specimens in the Wagner Free Institute tiiat 

 there existed in Florida during probably Plistocene time, a species of 

 horse of considerably smaller size than either the E. major, E. interme- 

 dins or E. occidentalis, and characterized by an enamel plication of the 

 molars similar to that of the E. intermedius, that is, generally a little more 

 complex than is characteristic of the E. caballus. What characterizes it 

 especially is the small size of the protocone, which has an anteroposterior 

 diameter considerably less than in the species named, not differing much, 

 however, from some specimens of the common horse. Thus this meas- 

 urement enters the anteroposterior diameter of the grinding surface 2.;") 

 times, rarely twice and one-third times, and in one instance onl)% twice. 

 In the true molars of E. intermedius, E. occidentalis and E. major the 

 proportion of the two diameters is 1 to 1.5 in the great majority of teeth. 

 This peculiarity with that of the incisors indicates, I think, that this horse 

 must be regarded as a distinct species or race. 



The part of the mandible referred to contains all the incisors, and the 

 second and third molars of the left side. The latter teeth agree with the 

 largest separate teeth of the collection in characters. The length of the 

 jaw anterior to the p. m. iii is equal to that of the Corresponding \y\Yl of 

 the E. intermedius and is considerably shorter than in the E. caballus. 

 It must be borne in mind that the molars are smaller than in the ordinary 

 Equus caballus, so that this dimension is relatively longer than in the 

 E. intermedius. Appropriately the symphysis is not so wide at the exter- 

 nal incisors as in the latter, and is less contracted at the posterior part of 



