288 ON THE NATURE OF EDESTUS AND RELATED FORMS. 



development of the base. In fact, about all that remains of the crown in Edestus 

 is the apical portion, the two processes corresponding to the buttressed lateral faces 

 of Campodus appearing as slender, pointed processes, which soon lose themselves 

 in the root (sheath). The type species of Edestus is also the least compressed from 

 side to side of the series. 



Information regarding the mode of growth of Edestus is afforded by the de- 

 tached segments of E. heinrichi and E. minor which are known. Successional teeth 

 are formed in the same way as in Campyloprion and Helicoprion, the only difference 

 being that the bases of the newer-formed segments ensheathe the older to a much 

 greater extent. The first-formed or "terminal segment" of E. heinrichi is not a "solid 

 bone" as stated by Newberry ('88, p. 120), but possesses a gouge-like base like the 

 rest. In the specimen figured by him as a supposed terminal segment, only the 

 "denticle" (crown) is preserved, and the carbonaceous matrix which originally filled 

 the interior of the sheath might readily be mistaken at first sight for vasodentine. 

 A few specimens exist in which the mode of succession is clearly discernible, perhaps 

 the best preserved being that recently figured by the writer (:02, p. 76), the original 

 of which is preserved in the Museum of Comparative Zoology at Cambridge. It is 

 interesting to note that the first to have discovered detached segments of Edestus 

 and to have commented upon their arrangement although reversing the relations 

 of anterior and posterior was Orestes H. St. John (:02, p. 658), who was familiar 

 with both E. minor and E. heinrichi. 



II. BIBLIOGRAPHY. 



Cope, E. D. 



'75. The Vertebrates of the Cretaceous Formations of the West. Report U. S. Geol. Survey, Territories, 



vol. 2, 302 pp., 57 pis. 

 Dean, B. 



'98. On a New Species of Edestus, E. lecoutei, from Nevada. Trans. New York Acad. Sci., vol. 16, pp. 



61-69. 

 Eastman, C. R. 



:00. Karpinsky's genus Helicoprion. Amer. Nat., vol. 34, no. 403, pp. 579-582. 

 Eastman, C. R. 



:01. On Campodus, Edestus, Helicoprion, Acanthodes, and other Permo-Carboniferous Sharks. Science, 



n. ser., vol. 14, p. 795. 

 Eastman, C. R. 



:02. Some Carboniferous Cestraciont and Acanthodian Sharks. Bull. Mus. Comp. Zool. Harvard College, 



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: 00. Ueber die Natur der Edestiden, mit besonderer Riicksicht auf die Gattung Helicoprion. Sitzb. kais 



Akad. Wiss., Wien, math.-naturw. Cl., Bd. 109, Abt. 1, pp. 5-9, 1 Taf. 

 Hitchcock, E. 



'56. Account of the Discovery of the Fossil Jaw of an extinct Family of Sharks, from the Coal Formation. 

 Proc. Amer. Ass. Adv. Sci., 1855, pp. 229-230. 



