152 [Feb., 1847. 



of Philadelphia, accurate figures of similar teeth with fragments 

 of the lower maxilla. The teeth being hollow, and, in his opinion 

 presenting other important differences, he constituted for them a 

 new genus, "Dorudon." 



The " Hydrarchos," I believe, has passed away without advancing 

 our knowledge upon this interesting subject, excepting perhaps that 

 Prof. Wyman discovered in the extremity of the ribs some ceta- 

 cean characters. 



The next important development consisted in the publication by 

 Professor Emmons, in the American Quarterly Journal of Agricul- 

 ture, beautiful figures of the teeth, anterior portion of lower max- 

 illae, together with a portion of the ramus having the coronoid pro- 

 cess and condyle almost perfect, cervical and caudal vertebras, and 

 a rib. But up to the present time, no notice has appeared of the 

 discovery of any considerable portion of the cranium proper for 

 the mutilated head of the so called Hydrarchos can scarcely be con- 

 sidered an exception. 



Early in January I was presented by F. S. Holmes, Esq., with 

 a portion of the left upper maxilla, containing one tooth and the 

 alveolse of several others, which he discovered in the Eocene beds 

 of Ashley river, about ten miles from Charleston. Soon after, Prof. 

 Lewis R. Gibbes, of the College of Charleston, visited the same lo- 

 cality, and had the good fortune to find the rest of the scull, much 

 fractured, but so carefully were the fragments collected, that with 

 a little patience we were enabled to restore them to their proper 

 places. It is then altogether to these gentlemen that we owe a 

 knowledge of this valuable fossil. 



Description. Occipital bone somewhat semicircular, transversely 

 flat or slightly concave, central portion thin ; a crest-like ridge sur- 

 rounds the superior portion terminating in the suture with the tem- 

 poral bone. Condyles two, articulating surfaces lunate, and almost 

 enclosing the foramen magnum. Foramen magnum oval ; trans- 

 verse diameter 1J inches, vertical diameter 1 inch; transverse pro- 

 cesses thick, spreading, making the breadth of the base of the cra- 

 nium equal to its diameter across the zygomatic processes ; jugular 

 foramen inch in diameter ; temporal bones small, mastoroid por- 

 tion thick and strong but not prominent ; articulating cavities for 

 condyles of lower maxillae large, forming about 30 of a circle, in- 

 clining inwards and backwards; maxillse thick and strong, vertical 

 section triangular; a cavity for nerves and vessels runs within at 

 the points of the roots of the teeth ; alveolar process thick ; palatal 

 bone strong, anteriorly emarginate and horizontal, posteriorly de- 

 scending below the alveolar process. 



Frontal bone and anterior portion of maxillae wanting ; walls of 

 the nasal canal smooth ; sutures squamous ; in the left maxilla one 

 tooth remains, which is solid, spear-shaped, edges coarsely ser- 

 rate, exterior side flattened, interior side convex ; agreeing in this 

 respect with the position of the teeth in the shark ; roots double, 



