220 FOSSIL FISHES OF THE ENGLISH CHALK. 



finely denticulated, but three well-marked, acute denticles behind. The vertical 

 wrinkling of the crown is here confined to the lateral portions. A posterior tooth 

 in the type specimen (fig. 3 c) is more strongly marked with vertical wrinkles than 

 the other teeth. Its principal cusp and its four or five pairs of lateral denticles are 

 low and broad cones, each with a sharp apex. 



In the type specimen the shagreen is shown to be diagonally fluted (fig. 3 d). 



Horizons and Localities. — Zone of Holaster mihglohosus : Snodland and 

 Wouldham, Kent. Apparently also from the Albian of Okeford Fitzpaine, Dorset 

 (R. B. Newton, Proc. Dorset Nat. Field Club, vol. xviii, 1897, p. 76, pi. iii, 

 fig. 2), and from the Gault of Folkestone. 



3. Syuechodus illingworthi (Dixon). Plate XLVI, figs. 5 — 7. 



1850. Acrodiis illuujworthi, F. Dixou, Geol. Sussex, p. 364, pi. xxx, figs. 11, 12. pi. xxxii, fiLf. 9 



1887. Acrodus (.-') illiiujwoHhi, A. S. Woodward, Geol. Mag , [3] vol. iv, p. lOi. 



1889. Acrodus (/) lllimjworthi and Hijhodus {t) sp., A. S. Woodward, Catal. Foss. Fishes B. M. 



pt. i, pp. 277, 297. 

 1891. Stj)iecJiodus illinijworthi, A. S. Woodward, Proc. Yorks. Geol. Polyt. Sou., vol. xii, p. 6G, pi. ii, 



figs. 3—7. 



Type. — Two associated hinder teeth from the zone of Holadev suhglobostis. 



Specific Characters. — A species known only by teeth, which sometimes attain a 

 width of 3 cm. Main cusp and lateral denticles of the principal lateral teeth 

 short, stout, and obtusely pointed, all closely connected and marked by fine ridges 

 radiating from the apex. Lateral denticles tending to become obsolete in the 

 hinder teeth, where they are indicated only liy fine ridges radiating from the acute 

 longitudinal keel of the crown. 



Description of Specimens. — The type specimens are hinder teeth in which the 

 lateral denticles are not clearly differentiated ; and two other specimens figured by 

 Dixon are the broken middle portions of similar teeth. Two more examples of 

 such teeth, exhibiting the characteristic arrangement of the conspicuous ridges or 

 Avrinkles on the crown, are represented in PI. XLVI, figs. 5, G. In both of these 

 the crown bears a small, irregular excrescence at two or three points; and in the 

 second specimen (fig. (3) the outer and lower faces of the large root are Avell seen. 

 An associated set of teeth, from which five are selected for representation in 

 PI. XLVI, figs. 7, 7a, 7 t>, seems to belong to the antero-Iateral part of the dentition 

 of the same species. The coronal wrinkles or ridges on these teeth are as promi- 

 nent as those on the type specimens and similarly radiate from the series of 

 apices ; but they are fewer and less closely arranged, so that the enamel appears 

 smoother. The blunt principal cusp is more elevated, and the equally blunt 

 lateral denticles, in from four to six pairs, are well differentiated. In one 

 specimen a single small cusp occurs as an irregular lateral excrescence. 



