CCELORHYNCHUS. 193 



Verona.' As sliowii by Williamson,- however, its microscopical structure seems 

 to be that of a deimal spine. In the absence of any knowledge of its basal 

 termination, it may therefore be placed provisionally among Ichthyodornlites. It 

 is typically an Eocene fossil and ver}^ rare in the Chalk, 



1. Coelorhynchus cretaceus, Dixon. Plate XLI, figs. 8, 9. 



1850. Ccelorltynchtts cretaceus, F. Dixou, Geol. Sussex, p. xiii, pi. xxxii, fig. 10. 

 1888. Coelorliynchus cretacevs, A. S. Woodward, Proc. Geol. Assoc, vol. x, p. 330. 



l^ype. — Imperfect spine ; British Museum. 



Specific Characters. — Smaller than the type species, with smooth and rounded 

 or flattened longitudinal ridges. Straight and very slightly tapering. 



Description of Specimens. — A new drawing of the type specimen is given in PI. 

 XLI, fig. 8, with part of its ornament enlarged in fig. 8 a. It is broken at each 

 end, but is shown to have been very long and slender, with scarcely any tapering. 

 The central cavity is exposed at the f I'actures, but the characteristic ribbing of the 

 surface is well seen elsewhere. The ridges are nearly straight, not wavy, but they 

 sometimes bifurcate or become double for a short distance ; they are also 

 occasionally interrupted, and the bent tapering ends lie side by side. A transverse 

 section of another specimen, examined under a microscope (figs. 9, 9 a), exhibits 

 nearly the same structure as that of the Eocene G. rectus as described by 

 Williamson, loc. cit. ; but the constituent sectors are fewer, being not more than 

 twenty in number, and the clefts or spaces between them are larger. Minute 

 divergent tubules are seen in each sector, but the concentric banding is less well- 

 defined and there are no vacuities, except close to the central cavity. 



Hori-Mvs and Localities. — Zone of Hota.stcr snJxjlohosns : Sussex. Senonian 

 zone : Norwich. 



Sulclass ELAS310BBJNCHIL 



Order SELACHII. 



Suborder ASTEROSPONDYLI. 



Family Scylliid^. 



The small " dog-fishes " are represented by nearly complete specimens in the 

 Upper Cretaceous of Westphalia and of Mount Lebanon, but are known only by 

 fragments from the English Chalk. The teeth have a central cavity, as in the 

 Carchariidae. 



1 A. S. Woodward, Catal. Foss. Fishes B. M., pt. iv, 1901, p. 593. 



2 W. C. Williamson, Pliil. Trans., 1849, p. 471, pi. xliii, figs. 35—37, aud ibid., 1851, p. 667. 



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