HOPLOPTERYX. P.) 



ing in the original of PI. Ill, fig. 1, is relatively small and triangnlar in shape, with 

 a prominent anterior ascending process. It is ornamented like the operculum. 

 The interopercnlum {i<>2->-) is of remarkable extent, and more coarsely ornamented 

 with slightly radiating tul)erculated ridges. Nine l)ranchiostegal rays have been 

 distinctly observed (B. M. no. 4l»04o). 



The vertebral column comprises 10 (or perhaps 11) vertebra? in the al^dominal 

 region, and 14 vertel)ra3 in the caudal region. It is essentially similar to that of 

 Bevy.}', and the greater part of it, with imperfect arches, is shown in the original of 

 PI. IV, fig. 1. The foremost vertebral centra (wanting in fig. 1) are very short 

 and deep, without transverse processes, but with stout neural spines sharply pointed 

 at the upper end. The five posterior abdominal vertebrge, with centra as long as 

 deep, bear laminar transverse processes, which are inclined downwards as well as 

 outwards, and increase in size backwards. Their neural spines are antero- 

 posteriorly compressed, so appear very thin in side-vicAv in fig. 1. The ribs are 

 rather slender. The posterior al)dominal centra, like the caudals, are imj^ressed by 

 two large lateral pits separated by a broad median longitudinal ridge, which is 

 also impressed by smaller longitudinally-extended pits. The neural and hgemal 

 arches in the caudal region are stout and sharply inclined backwards ; and a speci- 

 men figured by Agassiz, torn, cit., pi. xiv d, fig. 3, shows the characteristic expan- 

 sion of the arches at the base of the tail. The penultimate and antepenultimate 

 hgemal spines seem to form stouter expansions than in Beri/,r. 



The pectoral arch is suspended from the cranium by a large post-temporal, of 

 which only a fragment is shown in PI. Ill, fig. 1, pit. The greater part of this 

 element is a thin vertical lamina, with curved and serrated upper Ijorder, 

 strengthened by a ridge on its inner face (PI. VII, fig. 1, 2>^^), and connected with 

 the epiotic by a slender Ijar (B. M. nos. P. 5688, P. 5094). It exhibits a 

 thickened articulation with the supraclavicle (scL), which is deeper than broad, 

 with a straight and thickened anterior border. The upper half of the sigmoidally- 

 bent clavicle (PL III, fig. 1, cL), above the pectoral fin, is expanded into a thin 

 lamina, which is about twice as deep as broad and ornamented with fine vermicu- 

 lating ridges — finer than those on the opercular bones. The long, rod-shaped post- 

 clavicle almost reaches the ventral border of the fish (B. M. no. P. 5(392). The 

 small scapula (PL III, fig. 1) is pierced by an oval foramen. The pectoral fin- 

 rays {pd.) are comparatively delicate, probably short and about eleven in number. 

 Of the pelvic fins only a fragment is shown in PL III, tig. 1 , piv. When apparently 

 complete, each is observed to comprise a stout spine and six articulated rays, the 

 latter scarcely if at all longer than the former. The dorsal fin (PL III, fig. 1, do.) 

 arises above the insertion of the paired fins, and was evidently not subdivided. Its 

 anterior portion consists of six spines, which gradually increase in length back- 

 wards, are longitudinally ridged or fluted, and are borne by very stout winged 

 supports. These spines are imperfect in the original of PL III, fig. 1, and in most 



