SUMMARY AND CONCLUSION. 141 



half of the cranial roof is bent downwards and has slipped partly beneath the 

 right half. The mouth is also opened, and the ventral part of the abdominal 

 region is displaced downwards. The large characteristic smooth maxilla (mx.) is 

 well seen, with part of the supramaxilla, and the ectopterygoid (ecpt.) and 

 quadrate (qu.) are exposed. The small upper postorbital cheek-plate seems to.be 

 subdivided by a vertical suture ; the large postorbital is also divided transversely 

 in its lower half, but this may be merely an accidental crack. The tubercular 

 ornament of the opercular bones is unusually extensive and dense. Remains of 

 the paired fins show their relative proportions. The enamelled fulcra in the 

 dorsal fin are slightly curved, forming a convexly arched border ; the closely 

 divided and articulated fin-rays seem to be complete, and resemble those of 

 L. mantelli (see PI. VII, fig. 7). Some of the anterior scales of the flank are 

 coarsely serrated in their lower half, but further back the corresponding scales do 

 not exhibit more than one denticnlation above the produced postero-inferior angle, 

 and this soon disappears at the beginning of the tail. From the produced angle, 

 and sometimes from the denticulation above, a faint oblique ridge extends forwards 

 over the scale. The upper slime-canal, which begins as usual on the third row of 

 scales below the dorsal ridge, descends and becomes a little irregular near the 

 dorsal fin. 



SUMMARY AND CONCLUSION. 



Little is added to our knowledge of the Wealden and Purbeck fish-fauna by 

 the fossils discovered in the corresponding formations on the European continent. 

 Even in the great collection described by Traquair, 1 from the Wealden of Bernis- 

 sart, Belgium, there is only one genus, the Macrosemiid Notaijogits, additional to 

 those represented among the English fossils. At Bernissart no Selachian remains 

 are known, but in north Germany- there are teeth and spines of Hybodus much 

 resembling those now described. In north Germany several tine specimens of 

 Lepidotas have also been discovered, 3 but of other ganoids there are only teeth 

 and fragmentary jaws, chiefly referable to Pycnodonts. 



So far as known, therefore, the fishes of the Wealden and Purbeck formations 

 are essentially Jurassic, and not mingled with any typically Cretaceous forms. 

 Most of them are, indeed, the specialised and evidently final representatives of the 

 Jurassic families to which they belong, and very few can be regarded as possible 

 ancestors of fishes which followed in Cretaceous and later times. 



1 E. H. Traquair, " Les Poissous Wealdiens cle Bernissart," Mem. Mus. Roy. Hist, Nat. Belgique, 

 vol. vi (1911), pp. 1 — 65, pis. i — xii. 



2 W. Dunker, Monographie der Norddeutschen Weaklenbildung. Brunswick, 1846. 



8 W. Bianco, " Beitrage zur Kenntniss der Gt&ttmig Lepidotus," Abhandl. geol. Specialk. Preussen 

 u. Thuring. Staaten, vol. vii (1887), pt. 4, pp. 1 — 84, pis. i — viii. 



