282 ON THE NATURE OF EDESTUS AND RELATED FORMS. 



grated forward," being located in at least one species "somewhere upon the head- 

 region, perhaps above or behind the eye." 



Trautschold ('84, p. 160) revives the original hypothesis of Leidy, and Miss Hitch- 

 cock agrees with both of these authors in recognizing the odontological nature of 

 Edestus. In a paper of which only abstracts have been published ('87, p. 260), she 

 compares these fossils with the intermandibular arch of Onychodus, and locates the 

 segments definitely in the mouth region. The reasons which invalidate her inter- 

 pretation have been pointed out by Newberry, Dean, and Karpinsky ('99, p. 446), 

 although a somewhat analogous position has been suggested by the latter in his dis- 

 cussion of Helicoprion. The Russian Director, as an alternative hypothesis to regard- 

 ing the thrice-coiled spirals of Helicoprion as caudal spines, advances the conjecture 

 that the whorls protruded freely from the mouth-cavity above the head in front, and 

 served as formidable weapons for defence and offence, each individual possessing 

 but a single organ of this kind. In an appreciative review of Karpinsky's memoir, 

 entitled "Helicoprion, Spine or Tooth?" A. S. Woodward (:00, p. 33) inclines to the 

 opinion that of the two rival theories regarding the nature of Edestus, that one is 

 the more plausible which claims them as dental structures. In support of this view 

 Dr. Woodward cites various examples of coiling amongst both crushing and piercing 

 forms of sharks' teeth, although admitting that "the conception of a gigantic shark 

 armed in both jaws with several series (whorls) of teeth, like those now described 

 under the name of Helicoprion, is indeed sufficiently startling." 



Following closely upon Woodward's critique, three short notices appeared, those 

 by Jaekel (:00, p. 147) and by Fuchs (:00, p. 6) affirming, and that by Klaatsch (:01, 

 p. 433) denying, its dental nature; and the form was also reported by Koken (:01, p. 

 225) as occurring in the Salt Range of India.* Helicoprion is compared by the first- 

 named author with Janassa, and directly referred to the Petalodonts, and by the 

 second it is held to be analogous to the existing Raja. Klaatsch, per contra (:01, 

 p. 433), asserts that "es besteht kein Grund fur die Annahme, dass die Helicoprion- 

 Stacheln in der Mundregion gesessen haben." This author puts forward the ex- 

 traordinary proposition that the segments were not coiled during the life of the 

 creature, the spiral form having been brought about by posthumous deformation, 

 a speculation that may be dismissed without further comment. 



Some comparisons with Palaeozoic coiled teeth were made by the present writer 

 (:00, p. 581) in still another review of Karpinsky's memoir, and although he rejected 

 both of the Russian author's hypotheses, no new position was assigned for these 

 problematical bodies at that time. A year later, however, after a fortunate dis- 



* It is now known also from Japan (Yabe, :03, p. 3). 



