OPHIOPSIS. 73 



most of the scales being broader than deep, and those near the ventral border 

 especially so. On all the scales the inner vertical rib is feebly marked and wide, 

 and in the principal scales (fig. 1 b) the peg-and-socket articulation behind this rib 

 is wide and shallow. The caudal scales (fig. 1 c) are not united by peg-and-socket. 

 In the abdominal region the lateral line traverses about the eighth row from the 

 dorsal, the twelfth or thirteenth row from the ventral border. The exhibited outer 

 face of the ventral scales is smooth and slightly concave, and the hinder margin 

 seems to have been feebly serrated. There are no enlarged ridge-scales. 



A more imperfect and slightly larger specimen obtained by Mr. R. F. Damon 

 from the Purbeck Beds of the Isle of Portland (Brit. Mus. no. P. 8375), evidently 

 belongs to the same species and shows a few additional features. The premaxilla, 

 as usual in Oplnopsis, is relatively large and much expanded. The vertebras in 

 the abdominal region are complete cylinders about as long as deep, and the short 

 ribs are remarkably slender. Each of the stout rays of the dorsal fin bears a 

 small and slender pointed prominence directed backwards at its lower or articular 

 end (PI. XVI, fig. 2). The scales are smooth, and some of them exhibit very fine 

 and delicate serrations on the hinder border. 



Another imperfect fish of the same species from the West Quarry, Ridgeway, 

 near Weymouth, now in the Dorset County Museum, shows the small upper 

 circumorbital plates ornamented with large flattened tubercles of ganoine. A 

 displaced fragment of bone bearing minute teeth seems to be part of the 

 splenial. 



Horizon and Locality.— Lower Purbeck Beds: near Weymouth, Dorset. 



2. Ophiopsis breviceps, Egerton. Plate XVI, figs. 3 — 12. 



1852. Ophiopsis breviceps, P. M. Gr. Egerton, Figs, and Descript. Brit. Organic Remains (Mem. G-eol. 



Surv.), dec. vi, no. 6, pi. vi. 

 1895. „ „ A. S. Woodward, Catal. Foss. Fishes B. M., pt. iii, p. 170. 



Type. — Nearly complete fish ; Museum of Practical Geology, London. 



Specific Characters. — A robust species about 12 cm. in length. Length of head 

 with opercular apparatus about equal to maximum depth of trunk, which is twice 

 as great as depth of caudal pedicle and contained about four and a half times in 

 total length of fish. External head-bones coarsely tuberculated or rugose ; marginal 

 teeth long and slender. Dorsal fin occupying greater part of hinder two-thirds of 

 back, with about 35 rays, of which the longest do not equal the depth of the trunk 

 at their point of insertion ; pelvic fins arising almost at the middle point between 

 the pectorals and the caudal. Scales smooth and somewhat concave externally, 

 with a strongly but finely serrated hinder border. 



10 



