Reviews — Karplnshy on Helico^jrion. 35 



granular calcifications of Elasnioln-anch cartilage,^ whiuii aro often 

 mistaken for shagreen by palaeontologists. 



Having described the new fossils and determined their generic 

 and specific characters, Dr. Karpinsky concludes with a most 

 exhaustive discussion of their true nature, which is facilitated by 

 the concise sketch of our previous knowledge of Edestns, given 

 as an introduction to the memoir. He regards four results as 

 established : (i) that Helicoprion belongs to an Elasmobranch ; 

 (ii) that the bases of all the segments of the spiral were embedded 

 in the soft parts of the fish ; (iii) that the spiral must have been 

 situated in the vertical median plane of the fish ; and (iv) that the 

 whole of the spiral, except the large end, must have been exposed. 

 In a diagrammatic sketch he represents the problematical fossil as 

 originating in the upper jaw, and curling forwards and upwards so 

 that the spiral forms a terrible weapon above the snout. On this 

 supposition, each individual would possess only a single weapon of 

 the kind. 



In connection with the last-mentioned circumstance, it would be 

 interesting to know whether the five examples of Helicoprion 

 discovered in the quarry near Krasnoufimsk were found close 

 together at one time, or whether there is any other evidence of 

 their natural association. For a recent discovery by Dr. Traquair 

 in the Lower Old Red Sandstone of Turin Hill, Forfarshire,- proves 

 undoubtedly that there were Palaeozoic sharks with sharp, piercing 

 teeth, which were never shed, but became fused into whorls as the 

 animal grew. If he be correct, the teeth in these Lower Devonian 

 sharks even formed spirals ; for he considers that the so-called 

 Onychodas anglictis from Ledbury, figured in the Brit. Mus. Catal. 

 Foss. Fishes (pt. ii, pi. xv, fig. 1), truly belongs to the same Elasmo- 

 branch genus as the head from Forfarshire. It is well-known that 

 the crushing dental plates in the Elasmobranch Cochliodontidse 

 sometimes became considerabl}'^ in-rolled at the outer margin where 

 they could not break away.^ The discovery of Elasiuobranchs with 

 cutting or piercing teeth similarly disposed is therefore not surprising. 

 The fact that the known specimens of Edestns and Helicoprion are 

 bilaterally symmetrical does not necessarily relegate them to the 

 median line, if they happen to be whorls of teeth ; for several of 

 the anterior rows of teeth in the living Chlnmydoselache exhibit 

 essential bilateral symmetry.* Moreover, it may be remarked that 

 the possibility of Edestns and Helicoprion being whorls of teeth from 

 the mouth is not negatived by the absence of lateral facettes or 

 marks of contact with adjoining whorls : they may have been well 

 separated, as in the existing shark just mentioned. The conception 



^ Compare figiu-es by Williamsou, Phil. Trans., 18-51, pi. xxx, fijr. 29 ; and 

 A. Fritsch, " Faima der Gaskohle," vol. ii (1889), p. 101, tigs. 178, 180. 



^ R. H. Traquair, "Notes on Pala3ozoic Fishes": Ann. Mag. Nat. Hist. [7], 

 vol. ii (1898), p. 69 [Protodus scoticus, E. T. Xewton, sp.). 



^ P].g. Cochliudiis contorfHs, Ag. : J. W. Davis, Trans. Roy. Dublin Soc. [2], 

 Tol. i (1883), pi. Hi, figs. 4^, 5. 



* S. Garmau : Bull. Mus. Comp. Zool. Harvard Univ., vul. xii, Xo. 1, p. 6, pi. ii. 



