22 FOSSIL FISHES OF THE ENGLISH CHALK. 



The vertehral column is partly shown in PI. VI, and so far as preserved in this 

 and other specimens it closely resembles that of H. lewesiensis. The anterior 

 abdominal vertebrse are clearly destitute of transverse processes. The ribs are 

 rather stout (B. M. no. P. 7G53). 



The outer plate of the clavicle (PI. VI, cL) exhibits an ornament in its hinder 

 half as coarse as that of the operculum. The lower portion of the l)one is mucli 

 expanded into a transverse lamina (B. M. no. P. 9153). The pectoral fin seems to 

 have been as small and delicate as in H. leiresieiisi-^. The pelvic fin has a very 

 stout, ribbed anterior spine followed by seven articulated rays. Tlie bases of only 

 six of these rays are seen in PI. VI, ph., but the complete number is indicated in 

 PI. IV, fig. 2, |>/r. The dorsal fin is imperfectly known, but in the type specimen 

 its anterior portion evidently consists of about six very stout, ribbed spines, and 

 these are followed by at least seven equally stout articulated rays. The anal fin 

 comprises four ribbed spines and seven articulated rays (B. M. no. 394:i]). Of the 

 caudal fin only fragments are known. 



The scales are large, rather thick, and deeply overlapping ; and those of the 

 flank are deeper than broad. Their overlapped portion has a truncated anterior 

 l)order, towards which a few grooves radiate from the centre of the scale, as shown 

 in PI. VII, figs. 3, 4. Their exposed portion, wdien unabraded, is coarsely rugose 

 and strongly pectinated at the posterior border, as indicated in the same figures. 

 Their inner face bears a cluster of large, rounded tubercles, as shoAvn in the 

 counterpart of the type specimen (PI. VII, fig. 5). There are aljout 24 transverse 

 series of scales on the trunk, each comprising 10 or 11 scales, of which the sixth or 

 seventh above the ventral border is traversed by the lateral line. Some small scales, 

 as already mentioned, extend over a portion of the cheek ; and a few are seen 

 covering part of the antero-superior margin of the operculum (B. M. nos. 39431, 

 P. 7653^). 



The greater part of a unique slab of chalk in the Beckles Collection (B. M. no, 

 P. 9153), covered with remains of se^s'eral individuals of Boploptery.r siiperJms, is 

 shown of one half the natural size in the photograph, PI. V. These fishes seem to 

 have been suddenly destroyed and rapidly buried before there w^as much oppor- 

 tunity for decay. The principal specimen near the middle of the slab displays a 

 widely gaping mouth, and the head partly torn from the trunk. Nearly all the 

 specimens retain their original rotundity. A ventral view of the fish at the lower 

 border of the slab is given in PI. IV, fig. 2, already described. 



Horizons avd Localities. — Zones of Tilit/nclioiieJIa Cuvieri and Tcrehrtiiulina 

 (jracilis : neighl)ourhood of Lewes, Sussex. Probably same zones in Burham 

 district, Kent. 



