108 



Actmopterygii Isospondyli. 



Table-case, 

 No. 45. 



collection of nodules from the Upper Cretaceous of Brazil. 

 Of the existing American genus Lepidosteus, there are numerous 

 fragments of skulls, characteristic vertebrae, and scales from the 

 English Eocenes; and similar specimens are found both in France 

 and Germany. 



FIG. 153. Aspidorliynclius ornatissimus, Ag. ; Lithographic Stone, Bavaria. 



All the preceding fishes have a complex lower jaw, each half 

 consisting of at least four or five pieces ; and when the teeth 

 are powerful, those on the inner (or splenial) element are 

 specially well-developed. In all the following groups the lower 

 jaw consists normally of only two pieces on each side, one behind 

 (articulo-angular) and a larger piece (dentary) in front. 



Table-case, 

 No. 46. 



Table-case, 

 No. 15, and 

 Table-cases, 

 Nos. 47, 48. 



SUB-ORDER IV. Isospondyli. 



The first and earliest group of the higher fishes is that in 

 which the vertebras never fuse into a complex behind the head, 

 in which the simple air bladder is directly connected with the 

 gullet, and in which the pelvic fins are always situated well 

 behind the pectorals. Here may be placed the Pholidophorida? 

 which are remarkably like the herrings in general aspect, but 

 have only ring-vertebraa, ganoid scales, and fulcra on all the fins. 

 Pholidophorus itself ranges from the Khsetic to the Parbeck Beds, 

 but is especially well represented by a large series of specimens 

 from the Lower Lias of Lyme Regis. Some diminutive fishes 

 of the genera Peltopleurus (Upper Trias) and Pleuropholis 

 (Kimmeridgiaii and Purbeckian) exhibit a series of remarkably 

 deepened scales on the flank. The Oligopleuridse, ranging from 

 the Upper Jurassic to the Upper Cretaceous, come next. The 

 Leptolepida? follow, with Leptolepis, Aethalion, and Thrissops, 



FIG. 154. Leptolepis dubius, Blainv. sp. ; Lithographic Stone, Bavaria. [Scales omitted.] 



