2 Dr. H. Woodward — Note on an Ichthyodorulite — 



nous concretionary sandstone " (clay-ironstone) " in which the fossil 

 was bedded" (extract from Bev. J. G. Nicolay's letter to Lady 

 Barker, Government House, Perth, W.A., 13th July, 1883.) 



A carefully-prepared cast from the natural mould of the fossil 

 shows us in relief the curved outline of what may be estimated as 

 about three-fourths of the entire spine of a fish closely related 

 to Edestus Heinrichsii, of Newberry and Worthen, from the Coal- 

 measures of Belleville, Illinois, but of much smaller dimensions, less 

 robust, and more highly curved than the American species. 



We see in the Australian fossil 14 perfect flattened lancet-shaped 

 denticles, the cutting edges of which are crenulated along each 

 border (like the teeth of many of the Plagiostomous fishes) the 

 denticles being closely set along the outer curve of the spine, and 

 touching each other at their broadest expansion. They increase 

 gradually in size from one extremity of the fossil to the other. The 

 smallest denticle measures 3 lines in breadth, and 7 lines in length ; 

 the largest is 5 lines broad, and 11 lines in height. There is evidence 

 of the bases of one more denticle at the smallest end, and two more 

 at the largest end of the spine. The outer curve (which forms the 

 segment of a nearly true circle of 4|in. diameter) measures around 

 the points of the denticles 6|in., and on the inner margin of the 

 spine (following the curve in each case) 3J in. The breadth of 

 the spine with its denticle at the broadest end is 16 lines ; and at the 

 narrowest end 11 lines. The character of the American Edestus is 

 that the shaft of the spine is segmented throughout, and breaks up 

 into curved portions, each bearing a denticle ; these segments over- 

 lap to such a degree that the bases of the denticles are seen to curve 

 beneath each other, forming a series of raised imbricated ridges on 

 the sides of the spine, each curved ridge leading up to the base of 

 a denticle, as admirably shown by Prof. Leidy in his original paper. 

 The substance of the shaft of the spine of the Australian fossil must 

 have been much less massive than the American form, but was 

 evidently, like it, highly enamelled along its outer convex toothed 

 border, the hollows of the cast being all finely glazed. 



In the Proceedings Acad. Nat. Sci. of Philadelphia, vol. vii. Oct. 30, 

 1855, p. 414, Dr. Joseph Leidy gives the name Edestus vorax, to a 

 new genus of fishes, founded on a supposed fragment of a jaw with 

 portions of four teeth. In the Journal of the Acad. Sci. of 

 Philadelphia, Nov., 1856, 2nd ser. vol. iii. p. 159, Dr. Leidy 

 describes the specimen more fully, and figures it on plate xv. 

 " The fragment of jaw is six inches in length ; and it measures 

 three inches in depth from the dental border. The sides are 

 symmetrical, and slope divergently from the latter position towards 

 the base, which is convex and moderately keeled in the median line. 

 At the dental border the jaw is about seven-eighths of an inch in 

 thickness, and at the thickest part of its base measures one inch 

 and four-fifths. Longitudinally the base of the jaw is slightly 

 concave and furrowed. The surface of the bone is covered with 

 fine vermicular, reticulating, broken ridges, assuming a striking 

 resemblance to Arabic writing. The most remarkable peculiarity 



