1869.] Prof. Owen on Fossil Teeth of Equines. 



267 



coil by continuously heating the iron wire. In several experiments, by 

 employing twelve similar Grove's elements as a double series of six intensity, 

 an iron wire 1*56 millim. diameter was made bright red-hot ; and by keeping 

 the current continuous until the galvanometer-needles settled nearly at zero, 

 and then suddenly disconnecting the battery, the needles remained nearly 

 stationary during several seconds, and then went rapidly to about 10 : this 

 slow decline of the current during the first few seconds of cooling was 

 probably connected with the "momentary molecular change of iron wire " 

 during cooling which I have described in the preceding paper. The 

 irregularity of movement of the needles did not occur unless the wire 

 was bright red-hot, a condition which was also necessary for obtaining the 

 molecular change. 



The direction of the current induced by heating the iron wire was found 

 by experiment to be the same as that which was produced by removing 

 the magnet from the coil ; therefore the heat acted simply by diminishing 

 the magnetism, and the results were in accordance with, and afford a 

 further confirmation of, the general law, that wherever there is increasing 

 or decreasing magnetism, there is a tendency to an electric current in a 

 conductor at right angles to it. 



February 4, 1869. 



Dr. WILLIAM ALLEN MILLER, Treasurer and Vice-President, 



in the Chair. 



The following communications were read : — 

 I. "On Fossil Teeth of Equines from Central and South America, 

 referable to Equus conversidens, Equus tau, and Equus arcidens." 

 By Professor Owen, F.R.S. Received November 17, 1868. 



(Abstract.) 



The author, referring to his previous paper on the Equine fossil remains 

 from the cavern of Bruniquel, finds, in the preliminary illustrations of the 

 dental characters of existing species of the Horse-kind, the requisite and 

 much-needed basis of comparison for the determination of other fossils of 

 the Solidungulate group, and he devotes the present paper to the elucidation 

 of those which have reached him from Central and South America. 



He commences by referring to the type-specimens of teeth, from two 

 localities in South America, on which he founded the species E. curvidens, 

 describing it (in 1840) " as one coexisting with the Megatherium, Toxodon, 

 &c. in that continent, and which had become extinct at a prehistoric period." 



He then proceeds to describe more complete evidences of the dentition 

 of an allied extinct Horse discovered by Don Antonio del Castillo, 

 mining engineer, in newer Tertiary deposits of the Valley of Mexico. 

 Besides repeating the originally described characters of the curvature of 



VOL. XVII. x 



