996 



CLASS PISCES. 



is produced into a rostrum, occasionally equal in length to the 

 entire body ; this genus occurs in the Chalk of the Lebanon, and 

 is considered to show affinity with Opisthopteryx. Another group 

 seems to be related to the existing Clupeoid genus E/ops, but also 

 presents characters connecting it with the American freshwater 

 family Characinidce. Among these we may notice Rhacolepis, from 

 the Cretaceous of Brazil ; and in Europe Elopides, from the Lower 

 Eocene of Glarus ; Elopopsis, from the Cretaceous of Bohemia and 

 Istria ; Hemielopopsis, in which the borders of the mouth appear to 

 have been devoid of teeth, from that of Lesina, on the Dalmatian 

 coast ; and Protelopis, of the Bohemian Cretaceous, characterised 

 by the short jaws and the presence of crushing-teeth on the palate. 

 Thrissopater, again, from the Folkestone Gault, differs from the 

 modern Elopine type by its compressed body ; while PTalec, of the 

 European Chalk, is still very imperfectly known. A/osa, of the 



Fig. 935. — Skeleton of Diplomystus brevissimus ; from the Chalk of the Lebanon. 



Eocene of Algeria, and Diplomystus (fig. 935), originally described 

 from the Eocene of Wyoming, but subsequently found in the Creta- 

 ceous of Brazil and of the Lebanon, are allied forms. The latter 

 genus has a series of dorsal scutes, which are very characteristic. 

 Hemitrichias, from the Tertiary of Northern Italy, differs from all 

 existing Clupeoids in having two dorsal fins. 



Family Protosphyr^nid^. — With this family we come to the 

 first of a group comprising several families of extinct marine Fishes 

 characterised by their large spear-like teeth, and hence termed 

 Saurodonts. They should evidently be placed near the Clupeoids, 

 although their division into families must be regarded as provisional. 

 The present family is characterised by the production of the ethmoid 

 in advance of the maxilla, to form a long cylindrical rostrum ; by 

 the loose connection of the premaxillae with the maxillae ; and pro- 

 bably also by the complexity of the mandible. The teeth were 

 implanted in distinct sockets. The type genus Protosphyrcena 

 (Erisichthe) occurs in the Upper Cretaceous of both Europe and 

 North America ; and the large spear-like teeth of P. ferox % which 



