12 • FOSSIL FISHES OF THE ENGLISH CHALK. 



ring (an.). The iiiandil)iilar suspensorium and palato-pterygoid arcade are much 

 obscured ; but, so far as they are exposed, they resemble the corresponding parts 

 of the type species. The premaxilla {jwix.) lacks its hinder end on both sides of 

 the fossil, but displays the very large anterior ascending process. It has a sharp 

 lower edge, but a broad flattened oral face to bear a cluster of minute teeth. The 

 maxilla (mx.) is also imperfect on l)oth sides, but is represented on the right by 

 its anterior and posterior extremities. Its anterior end is turned uj) wards in a 

 stout process, while its posterior portion expands into a large, smooth lamina. 

 Only the hinder supramaxilla (suhv. 2) is preserved, and it may perhaps be a little 

 broken at its upper border. It is ornamented with a very conspicuous rugosity, 

 of which the main ridges extend antero-posteriorly. 1'he mandil)le appears exactly 

 as described in the type species, and the dentary (J.) is shown to have borne a l)road 

 band of clustered minute teeth. The hour-glass-shaped ceratohyal (fig. 2, cli .) is 

 short and deep, with a broad lamina of bone connecting its upper angles. It 

 (perhaps with the small epihyal, which is covered) supports fiA^e branchiostegal 

 rays {(>r.). The circumorbital plates {co.) are ornamented and deeply grooved, and 

 all except one are very small, as in B. elegans ; but the enlarged foremost plate of 

 the series, which is imperfect on the right side {ao.), is much less deepened than in 

 the latter species. Its maximum depth is indeed less than the vertical diameter of 

 the orbit, and, as shown on the left side, its lower border is feebly pectinated or 

 serrated. Abraded and broken rugose scales remain covering the cheek Ijehind 

 and below the circumorbital ring. The opercular apparatus closely resemljles that 

 of B. elcfjaiis, but is more strongly ornamented. In the fossil only three or four 

 of the scales which originally covered the operculum are preserved. Behind the 

 opercular bones, a little displaced and imperfect, are observed the characteristic 

 post-temporal (p^t-), supraclavicle (.yc/.), and clavicle (r/.,) Avith part of the scapula 

 (sc.) pierced by the usual oval foramen. The destruction of some scales also ex- 

 poses a few of the stout ribs (r.). The right pelvic fin (j'/r.) is shown slightly 

 liehind the pectoral arch. Its large and stout anterior spine is fractured and 

 fragmentary, but seems to have been as long as the succeeding articulated rays, of 

 which only four are seen. The anal fin spines (a.) are also very stout and slightly 

 ornamented Ijy longitudinal ridges. They seem to have been four in number, 

 rapidly increasing backAvards in size and length. The base of only one articulated 

 i-ay is preserved behind them in the fossil. The scales are relatively large, with a 

 gently and regularly rounded posterior border. The abraded rugose ornament of 

 their exposed portion has often a pitted appearance, but at the posterior border it 

 passes into regular ])ectinations. The scales cannot be exactly counted, but there 

 were probably less tlian 20 of them in any transverse series on the abdominal 

 region. The lateral line (//.) forms a little smooth triangular ])rominenee on the 

 covered portion of each scale which it traverses. 



Horizon and LocaJifij. — Pi'obaljly zone of Uolasfer p/fl»»,9.- C'uxton, Kent. 



