194 FOSSIL FISHES OF THE ENGLISH CHALK. 



Genus SCYLLIUM, Cuvier. 



Scyllium, G. Cuvier, Rc'giie Animal, vol. ii, 1817, p. 124. 

 Thyellina, L. Agassiz, Poiss. Foss., vol. iii, 1843, p. 378. 

 Sci/lliodas, L. Agassiz, ihid., p. 377 (in part). 



Oeneric Characters. — Anterior dorsal fin above or behind pelvic pair ; origin of 

 anal always in advance of tliat of tlie posterior dorsal fin ; npper edge of candal 

 fin without enlarged dermal spines. Teeth small and delicate, each with a middle 

 cusp and generally one or two pairs of conspicuous lateral denticles ; several series 

 in function at one time. 



Ti/j)e Species, — The existing Scyllium canicnla, common on the British coast. 



I. Scyllium antiquum (Agassiz). Plate XLII, figs. 1—4. 



1843. ScylUodus antiquus, L. Agassiz, Poiss. Foss., vol. iii, p. 378, pi. xxxviii, figs. 1, 3 (non fig. 2). 

 1889. Scyllium antiquum, A. S. Woodward, Catal. Foss. Fislies B. M., pt. i, p. 340. 



Type. — Remains of head, etc., with teeth, from zone of Holaster snhglohosus ; 

 British Museum. 



Specific Characters. — Teeth with a slender acuminate crown and a single pair 

 of divergent, short, stout denticles. Inner coronal face in all teeth, and both faces 

 in those placed at the back of the jaw, vertically striated. Shagreen tubercles 

 leaf-shaped, flat and smooth. 



Description of Specimoii.^'nus, species is still known only by the type specimen, 

 which exhibits remains of the cartilages of the head, with very few teeth and some 

 of the anterior vertebrae. Each dental crown (PI. XLII, figs. 1 — 8) is rounded in 

 section and tapers rapidly to the sharp apex, without any sigmoidal bend; it is 

 Avide below, where it is flanked by a pair of short and stout, pointed denticles, 

 which are slightly divergent. The root of each tooth is very short but bifid, 

 appearing as a wide arch when seen from the outer face (figs. 1 — 3), with each 

 pedicle expanded at the base ; it projects far inwards, and its inner apex is pierced 

 by a large nutritive foramen (fig. 3 a) ; its lower, attached face is flattened. In the 

 anterior teeth (fig. 1 ) the outer coronal face is smooth, while the inner coronal face 

 and the whole face of both lateral denticles are marked with fine vertical striations. 

 In the posterior teeth (fig. 2) the outer coronal face is also conspicuously striated. 

 The figure of a tooth given hy Agassiz is inaccurate and misleading. 



In the vertebral centra there appears to be no calcification outside the primitive 

 double-cone except a single peripheral layer. 



A few traces of shagreen occur (PI. XLII, fig. 4) as shining, leaf-shaped . 

 tubercles, all flat and smootli, Avith a small cruciform Ixise at one end. 



Horizon and LocdJity. — Zone of Hnla.^fer snhijlohnsits : Bui'haui, Kent. 



