344 



A SPIDORHYNCHIDAE 



order ; very possibly Lepidoateus is merely a specialised late 

 remnant of the family Semionotidae. 



Family LEPIDOSTEIDAE. 



Lcpidosteus, Lac. ; Eocene, Europe ; Eocene and living, North 

 America (Fig. 324). 



IXCERTAE SEDIS. 



Family ASPIDORHYXCHIDAE. Certain Mesozoic fishes, with very 

 elongate body (Fig. 320), and a sharp long snout formed by the upper 

 and lower jaws, are included in this family (Reis [349], A. S. Woodward 

 [505], Assmann [21]). There are deep rhombic ganoid scales, with peg 

 and socket articulations. Ganoid bones cover the skull ; a large cheek- 

 plate protects the side of the head; there are several lateral but no 

 median gulars. The very long upper jaw is formed by the premaxillae 

 and a portion of the maxillae which are in several pieces. The shorter 

 lower jaw is provided with a distinct predentary bone. Sharp teeth are 

 set on the jaws and palate. The nostrils are immediately in front of 



Kin. 325. 



AspidorhyiicUus acutirostris. Blainv. ; Upper Jurassic, Bavaria ; restored. 

 (After A. S. Woodward.) 



the orbit. A short dorsal fin is opposed to a similar anal, and the caudal 

 is quite homocercal in appearance (Fig. 325). Small fulcra are found 

 only on the median fins. The Aspidorhynchidae are placed as a rule 

 near the Lepidosteidae, which they resemble in the subdivision of the 

 maxilla and absence of a median gular plate. But they differ from 

 them in many important characters, such as the position of the nostril, 

 the shape of the tail, and the possession of simple annular vertebral centra. 

 On the other hand, they approach the Pholidophoridae in these same 

 characters, and they also have a median vomer as in all Teleostei. 

 Possibly they represent a specialised offshoot from some eai'ly Amioid stock. 

 Aspidorhynchus, Ag. (Fig. 325) ; Jurassic, Europe. Belonostomus, Ag. ; 

 Cretaceous, Europe, Asia, America, Australia. 



Order 3. TELEOSTEI. 



Almost all the living Osteichthyes are included in this the 

 highest Order of fish. The typical Teleostei are characterised by 

 certain modifications of which the chief are the following : the loss 

 of the ganoine covering the exoskeleton ; the rounded thin over- 

 lapping scales ; the simple annular or amphicoelous bony vertebral 



