108 



ActiuopteyiJCjLi — lso.<'po)i(lijU 



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 vertebrtfi, and scales from the 

 English Eocenes; and similar specimens are fotmd both in France 

 and Germany. 



Fig. ioS.—Agpidorhiinchas ornKtissniius, Ag. ; Lilhogriiphic Stone, Bavaria. 



All the preceding fishes have a complex lower jaAv, 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 vertebra? 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 Pholidophoridae 

 which are remarkably like the herrings in general aspect, but 

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

 PhdlidopJiiirus iiseli ranges from the Rhtetic to the Purbeck 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 Pelioplcums (Upper Trias) and Pleiiropholis 

 (Kimmeridgian and Purbeckian) exhibit a series of remarkably 

 deepened scales on the flank. The Oligoplenridse, ranging from 

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

 LeptolepidiB follow, with Leptolepis, Aethalion, and Tlirissops, 



^i^ 



■■■^ 



Fig. \:A. — Icptolcpis ihihiu.^, Blainv. sp. ; Litliographic Stone, Bavaria. [Scales omitteil.] 



