Remarks on Bathygnathus horealis. 

 By Joseph Leidf, M.D. 



A PAPER by the author, published in this Journal in 1854, gives an account of 

 an interesting fossil from the red sandstone of Prince Edward's Island, described 

 under the name of Bathygnathus horealis. The specimen, now preserved in the 

 museum of our Academy, consists of one side of a jaw with teeth imbedded in a 

 slab of red sandstone, and is well represented in the chromo-lithographic plate 

 accompanying the paper mentioned. 



Prof. Owen, in a paper published in the Quarterly Journal of the Geological 

 Society of London for 1876, has referred Bathygnathus, together with a number of 

 other extinct genera of reptiles from the Permian formations of the Urals and 

 South Africa, to an order under the name of Theriodonts. In my understanding 

 of the characters of this order so far as they are derived from the teeth, it would 

 appear that in their differentiation, arrangement, and mode of insertion in the 

 jaws they exhibit mammalian affinity, especially to the carnivores, more than 

 usual among reptiles, and hence the name of Theriodonts. Though such may be 

 the case with the more immediate representatives of the order, it seems to me the 

 characters do not apply to Bathygnathus, not even so much as in crocodiles. 



In my description of Bathygnathus Prof. Owen has pointed out, what now 

 appears to me to be a most egregious blunder, the reference of the fossil to the 

 mandible. Truly it appears to me to pertain to the upper jaw, and I can only 

 wonder at my mistake. In some other points Prof. Owen has misunderstood me, 

 and has fallen into error in regard to several anatomical features of the fossil. 



"The teeth," says Prof. Owen (p. 359) "are implanted in distinct sockets, and 

 have subcompressed, recurved, conical, acuminate crowns, with anterior and pos- 

 terior trenchant borders, of which the latter is minutely crenulated." This does 

 not exactly accord with my account, and I, therefore, redescribe them. 



The teeth have compressed, recurved, conical crowns with anterior and poste- 

 rior trenchant borders, both of which are distinctly crenulated. The borders are 

 directed to the inner aspect of the crowns, the faces of which are more or less 

 de|)ressed contiguous to the borders, especially behind. The teeth resemble those 

 of some of the recent Monitors and those of Megalosaurus, but are proportionately 



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