Prof. Owen on the Dichodon cuspidatus. 



185 



by a true premolar. Whilst, however, the Dichodon resembles the 

 Hog-tribe in the kind and number of its teeth, it resembles more 

 the Ruminantia in the configuration of the true molars. The now 

 ascertained facts of the deciduous dentition of the Dichodon supply 

 an additional test of its affinities, owing to the marked difference in 

 the times and order of succession of the permanent teeth, between 

 the non-ruminant and the ruminant Artiodactyles. 



In the Ox and Sheep the last true molar cuts the gum before any 

 of the premolars appear, and the canine teeth are the last to come 

 into place. In the Hog the canines appear before the premolars, 

 and these rise into place before the last molar has attained the level 

 of the other grinders. In the Dichodon the second true molar is in 

 place before any of the deciduous teeth have been shed ; and it more 

 resembles the Sheep in the order of appearance of the permanent 

 teeth. But there is some difference ; for by the time the second 

 true molar is as far advanced in development as in the Dichodon, 

 figured in plate 4 of vol. iv. Quart. Journ. of Geol. Soc, the first 

 permanent incisor is in place, and the germs of the premolars in the 

 formative cavities have calcified crowns. The adult Dichodon appears 

 to have equalled in size a South Down sheep : the probable age of the 

 immature individual above referred to might be surmised from the 

 analogies presented by the subjoined Table of the times of appear- 

 ance of the permanent teeth in the — 



Ox. Sheep. Hog. 



Early. 

 Year. Month. 



Early. 

 Year. Month. 



The symbols of the teeth are explained in the author's paper " On 

 the Homologies of the Teeth," in Reports of the British Association, 

 1848 ; and in Orr's ' Circle of the Sciences,' 8vo, 1854. 



The additional specimens of the Dichodon described in this paper 

 are from the Upper Eocene beds ; one from the Isle of Wight is pre- 

 served in the private collection of Dr. Wright of Cheltenham ; the 

 rest, from Hordwell, Hants, form part of the Collection of Fossils in 

 the British Museum. 



2. " On a Fossil Ophidian from Karabournou, Salonica Bay." By 

 Professor Owen, F.R.S., F.G.S. 



The vertebrae hei"e described, thirteen in number, indicated by 

 their size a serpent of between 10 and 12 feet in length. They were 

 discovered some years since by Capt. Spratt, R.N., in the fresh- 



