94 GUIDE TO THE FOSSIL REPTILES, AMPHIBIANS, FISHES. 
Wall-case from the Lithographic Stone of Bavaria; while the closely 
Table-case re ^ ate( ^ Belonostomus is both Upper Jurassic and Cretaceous 
21. (Table-case 21). Remains of species of the existing American 
genus Lepidosteus, or “ bony pikes,’’ are found in the Lower 
Tertiaries of Europe, and many of the characteristic concavo- 
convex vertebrae, with scales, are exhibited from the Upper 
Eocene of Hordwell, Hampshire. 
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 the following groups, on 
the other hand, the lower jaw consists normally of only two 
pieces on each side, one behind (articulo-angular) and a 
larger piece (dentary) in front. 
Sub-order 4.— Isospondyli. 
Wall-cases 
15 , 16 . 
Table-cases 
22 - 28 . 
Table-case 
22 . 
Wall-case 
15 . 
Table-cases 
23 , 24 . 
In the first and earliest group of the higher fishes 
the vertebrae never fuse into a complex behind the head, 
the simple air bladder is directly connected with the 
gullet, and 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 ganoid scales, fulcra on all the fins, and only 
ring-vertebrae. Pholidophorus itself ranges from the Rhaetic 
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 Pelto- 
pleurus (Upper Trias) and Pleuropholis (Kimmeridgian and 
Purbeckian) exhibit a series of remarkably deepened scales 
on the flank. The Oligopleuridae, ranging from the Upper 
Jurassic to the Upper Cretaceous, come next. The Leptolepidae 
follow, with Leptolepis, Aethalion , and Thrissops, mostly from 
the Lithographic Stone of Bavaria; and these differ from the 
herrings (Clupeidse) chiefly in the meeting of the parietal 
bones and in the simple character of the tail. Leptolepis 
(Fig. 102) is first represented by small species in the Upper 
Lias of England, France and Wiirtemberg. 
Either here or immediately after the “ Amioids ” (the 
Pholidophoridae having previously been classed with the 
“ Lepidosteoids ”), it has long been customary to recognise a 
break in the series of Teleostomatous fishes. All groups 
below have been united under the name of Ganoidei (enamel- 
scaled fishes); all above have been termed Teleostei (bony 
