44C ZOOLOGY. 



The bony fishes date back to the Jurassic period, but did 

 not become numerous until the Cretaceous and especially the 

 Tertiary Period. The Green River beds of Wyoming abound 

 in their remains. 



The Teleosts are divided into eight orders, in an ascending 

 series as follows : Opisthomi, Apodes, Nematognathi, Scyplio- 

 phori, Teleocephali, Pediculati, Lopliobranchii and Plectog- 

 nathi. 



Order 1. OpiMomi. The fishes of this group are char- 

 acterized by the separation of the shoulder-girdle from the 

 head. The ventral fins are either abdominal or wanting. 

 The typical genus is Notocantlius, in which the body is elon- 

 gated, with a proboscis-like snout. 



Order 2. Apodes. In this group, also, the scapular arch 



Fig. 403. Common Eel, Anguitta, acutirostris. 



is free from the skull, while the maxillary bones are rudi- 

 mentary. The branchial apertures are unusually small, and 

 there are no ventral fins, while the body is very long, cylin- 

 drical, snake-like. The order is represented among many 

 other forms by the common eel (Anguilla), the conger-eel, 

 and the Murcena of the Mediterranean Sea. The conger-eel 

 (Conger oceanicus Gill) ranges from Newfoundland to the 

 West Indies. Gill, as well as Giinther and others, regards a 

 long transparent ribbon-like fish, described under the name 

 of Leptoceplialus as the young of the conger-eel. 



The common eel, Anguilla acutirostris (Fig. 403), occurs 

 on both sides of the Atlantic, on the North American coast 

 as far south as Cape Hatteras, and in inland rivers and lakes. 

 The sexes do not differ externally, and internally only 



