CTENOTHRISSA. 83 



front border, where it is deepest. The inner face (PI. XVII, fig. 6) is smooth' 

 with a slight thickening at the hinder margin, where the fine pectinations of the 

 outer face are just evident. The lateral line traverses the ninth scale of each 

 series above the bent ventral scale. It is marked by a row of short prominent 

 ridges, each widest at the front of the exposed area of the scale on which it rises 

 and tapering to a point behind. The ridges often exhibit irregular longitudinal 

 flutings, as already noticed by Agassiz. 



Horizons and Localities. — Zones of Holaster subglobosus to Terebratulina gracilis : 

 neighbourhood of Lewes, Sussex. Zone of Holaster subglobosus : Glynde, Clayton, 

 and Arundel, Sussex ; Dorking, Surrey ; and Burham, Kent. 



2. Ctenothrissa microcephala (Agassiz). Plate XVIII, figs. G — 9; Plate XIX, 



figs. 1, 2. 



1835-38. Beryx microcephalus, L. Agassiz, Poiss. Foss., Feuill., p. 55, and vol. iv, pp. 4, 119, pi. xiv b, 



figs. 3—6 ; pi. xiv c, fig. 10. 

 1850. Beryx microcephalics, F. Dixon, Geol. Sussex, p. 372, pi. xxxiv, fig. 3. 

 — Beryx radians, F. Dixon, ibid., p. 371, pi. xxxvi, fig. 4 (errore). 

 1888. Beryx microcephalus, A. S. Woodward, Proc. Geol. Assoc, vol. x, p. 327. 



899. Ctenothrissa microcephala, A. S. Woodward, Ann. Mag. Nat. Hist. [7], vol. iii, p. 491. 

 1901. Ctenothrissa microcephala, A. S. Woodward, Catal. Foss. Fishes B. M., pt. iv, p. 124, pi. \, 

 figs. 5, 6. 



Type. — Distorted head and abdominal region from one of the Turonian zones ; 

 British Museum. 



Specific Characters. — An elongated species, attaining a length of about 15 cm. 

 Length of head with opercular apparatus equal to the maximum depth of the 

 trunk, which is contained about twice in the length from the pectoral arch to the 

 base of the caudal fin. Head as in C. radians, but operculum nearly smooth and 

 almost covered with thin scales. Pelvic fins apparently less elongated than in 

 G. radians. Scales very large, the lateral line extending along the fourth series 

 above that which forms the ventral border of the flank ; serrations comparatively 

 coarse, and no tubercular ornament in front of them. 



Description of Specimens. — The type specimen in the Mantell Collection (no. 

 4034) exhibits only fragmentary remains of the head with part of the characteristic 

 squamation. The lower portion of a head and trunk in the same collection, also 

 figured by Agassiz {torn, cit., pi. xivc, fig. 10), displays equally characteristic 

 scales, with traces of the pelvic, anal, and caudal fins, and some fragments of the 

 head-bones. The general proportions of the fish, noted in t lie specific diagnosis, 

 are better shown by the specimens figured by Dixon and those referred to in the 

 British Museum Catalogue. 



