AULOLEPIS. 87 



teeth (seen in B. M. no. 47932) resemble those of the upper jaw. The antorbital 

 plate of the circmnorbital ring, imperfect in the original of fig. 3 (ao.), is smooth, 

 but marked by downwardly radiating branches from the slime-canal which traverses 

 it. Smooth cycloidal scales extend over the postero-inferior part of the cheek. 



The opercular apparatus is unornamented, and the operculum (op.) is clearly 

 covered with scales. The narrow preoperculum (pop.) is sharply bent at the angle, 

 and the lower limb is about two-thirds as long as the ascending limb. The bone 

 is expanded at the angle, where a few radiating ridges mark diverging branches of 

 the slime-canal. 



Vertebras are seen in the caudal part of the type specimen, while scattered 

 remains of them occur in the original of fig. 3 and in other fossils. They are 

 rather small and cannot have been less than 35 in total number. The centra are 

 strengthened with delicate longitudinal ridges. The hasmal spines at the base of 

 the caudal fin are stout and expanded, but do not appear to have been fused into a 

 hypural plate. 



The clavicular arch (seen in B. M. no. 49883) is shaped as in Otenothrissa 

 radians (p. 81), but the post-temporal is unornamented. The smooth post-clavicle 

 is clearly overlapped by the clavicle (B. M. no. 49883). The scapula (shown 

 in Proc. Zool. Soc, 1894, pi. xliii, fig. G) is broader than deep and pierced 

 by an oval foramen. The small and delicate pectoral fin (fig. 3, pet.) seems to 

 have comprised about twelve rays. Bach pelvic fin consists of nine comparatively 

 stout rays, of which only the bases are usually preserved (fig. S,plv.). The anal 

 fin is fragmentary in the original of fig. 3 (a.) ; but more satisfactory remains in 

 B. M. no. 47932 show that it was quite small and short-based, its elevation probably 

 not exceeding half the depth of the trunk at its insertion. It arises somewhat 

 nearer to the caudal fin than to the pelvic pair. The dorsal and caudal fins are 

 only known by a few fragments of rays. 



The scales are so large that there would probably be only about ten in each 

 transverse series on the flank, though the number is uncertain. They are all 

 rather thick, and quite smooth or only marked by the fine concentric lines of 

 growth. The ordinary scales (fig. 3 b) have a rounded or almost bent hinder 

 margin, their exposed area being nearly rhombic in shape and somewhat deeper 

 than broad. Those of the lateral line (fig. 4), which seem to form the fifth or sixth 

 longitudinal row from the ventral border, are truncated behind, and marked by the 

 prominent, smooth ridge of the slime-canal, which is always widest in front and 

 pointed behind. The ridge of the lateral line is conspicuous along the whole 

 length of the fish from the post-temporal plate to the base of the caudal fin. When 

 seen from inside, the scales exhibit the peculiar thickening of the hinder margin 

 already noted in Gtenothrissa radians (p. 83). 



Horizons and Localities. — Turonian zones : neighbourhood of Lewes. Zone of 

 Ilolaster subglobosus : Burham, Kent ; Dorking, Surrey. 



