154 On the Zeuglodon. 



Tcacter whatever of a reptile. No reptile has as yet been dis- 

 covered having teeth with double roots implanted in corre- 

 sponding sockets; the Hydrarchos has teeth with double roots 

 and double sockets. In reptiles the bodies of the vertebr;i; 

 are either concave on one face and convex on the other, or 

 else doubly concave ; the faces of the vertebr;© of the Hy- 

 drarchos are flat as in mammalia. The size of the vertebral 

 canal compared with the bodies, has, in the Hydrai'chos, the 

 Mammalian and not the Reptilian proportions. 



If any doubt heretofore existed, it is now removed by the 

 recent discovery by F. S. Holmes, Esq., and Professor Lewis 

 R. Gibbs, of Charleston, South Carolina, of a skin of the Zeu- 

 glodon nearly entire, and which demonstrates that ^e restored 

 head given by Carus is purely imaginary (and with this state- 

 ment any one will be satisfied who will take the trouble to com- 

 pare the figures). The newly discovered skull, in addition to 

 the character given above, has the double occipital condyles, 

 only met with in Mammalia, and the convoluted tympanic bones 

 which are characteristic of Cetaceans. (See American Jour- 

 nal of Science, September 1847). The bones of Koch's Zou- 

 glodon are now in Berlin, and a report on them is in prepara- 

 tion, to be presented to the Academy of Sciences by Professor 

 Muller, the most distinguished German physiologist. In a 

 letter to Retzius of Stockholm, recently published, he says, — • 

 " I think I can satisfactorily shew that the Hydrarchos is not 

 a reptile, but a mammal belonging to a peculiar extinct family. 

 It has the ear formed as in the mammals, viz. : — a helix con- 

 structed as in the mammalia, with a tympanic bone as in tlie 

 whale. It has, moreover, two occipital condyles, and, in the 

 whole formation of the cranium no trace of a reptile struc- 

 ture occurs, but, on the contrary, everything is as in the 

 mammals." 



From this review of the evidence in the case, the two fol- 

 loAving propositions, given in a former report, are sustained. 



\st. The skeleton of the Hydrai'chos is composed of bones 

 belonging to two different individuals. 



2f/, The bones are those of a Mammal. In addition to the 

 above, it may now be added, 



3rf, That they are intimately allied to those of Cetaceans. 

 —J. W. {Boston Journal, September 30, 1847.) 



