On the Stnicture ami 113 



Till. — On the Structure mid Relations of Edestus, with a 

 Description of a gigantic neiu Species. 



BY J. S. DEWBERRY. 

 Read January 16, 1888. 



The first of the remarkable group of fossils now included in 

 the genus Edestus, was brought to the notice of scientists by 

 Dr. Joseph Leidy, in his description of Edestus vorax ; Journal 

 of the Academy of Natural Sciences of Philadelphia, Series 2, 

 Vol. Ill, p. 159, PI. XV, 1856. The type-specimen was only a 

 fragment of an organ that must have had a length of a foot or 

 more, by four inches in width and one and a half inches in 

 thickness. The portion figured by Prof. Leidy, seems to have 

 come from about the middle, and consists of a mass of bone 

 composed of a series of segments, eacli one of which carries at 

 its upper margin an enameled, compressed, triangular, crenu- 

 lated denticle, one and a half inches in height and breadth. In 

 general aspect these denticles considerably resemble the crenu- 

 lated teeth of Carcharodon, but with th's marked difference ; 

 that like all the cutting teeth of sharks, these latter are flat- 

 tened on one side and arched on, the other, and terminate below 

 in a bony base that had only a ligamentous attachment to a car- 

 tilaginous jaw ; hence in death and decomposition the teeth 

 were generally separated and scattered. In Edestus, however, 

 the denticles are firmly anchylosed to a bony support. 



At the meeting of the American Association held in Provi- 

 dence in 1855, another and quite different species of Edestus 

 was exhibited by Prof. Edward Hitchcock, and was considered 

 by him to be 'Hhe jaw of a shark, but of very peculiar charac- 

 ter." Prof. Louis Agassiz, who was present, examined the spec- 

 imen and gave it as his opinion that it formed a part of the jaw 

 of a shark allied to the saw-fish. He stated that " the sword 

 of Pristis is originally composed of two bones, and if these 



