BONY FISHES AND GANOIDS. 493 



are right-eyed fishes, with the upper eye somewhat in front of the lower one, 

 and the narrow mouth twisted round to the left side ; the dorsal fin, which is 

 distinct from the caudal, starting on the snout. 



SUB-ORDER V. PHYSOSTOMI. 



Section A. Apodes. 



The bony fishes formhig the present group are broadly distinguished from 

 all the foregoing by the possession of a duct to the air-bladder when present; 

 such duct opening either into the oesophagus or the stomach. To this leading 

 and all-important internal feature of the group it may b? added, that exter- 

 nally all these fishes have the pelvic fins situated far behind the pectoral pair, 

 whence they are described as abdominal in position. If the skull be ex- 

 amined, it will be found that, as a general rule, the parietal bones meet in the 

 middle line. The rays supporting the fins are mostly soft, although the first 

 in the pectoral pair and dorsal are spiny. Most of these features are primi- 

 tive a duct to the air-bladder being found in the succeeding sub-orders of 

 the Teleostomi, which are clearly low types and it may accordingly be 

 inferred that the Physostomi are inferior in their organisation to the groups 

 in which the air-bladder is unprovided with a duct. The section named 

 above includes three families of eel-like fishes, but as the features by which 

 this section differs from those that follow are deep-seated and would require 

 a considerable amount of technical language for their adequate explanation, 

 they cannot be described on this occasion. 



The Murwnidm are all characterised by their snake-like bodily form, but as 

 this form is common to the other two families included in the section, other 

 features have to be relied on for the definition of the group. 

 Unfortunately, many of these features can only be observed The Eel-Tribe. 

 by an examination of the skeleton or internal soft parts. Family Murcen- 

 Externally eels are characterised by the absence of the pelvic idee. 



pair of fins, and in some forms the pectorals are likewise 

 wanting. If the dorsal and anal fins are developed, these either form with 

 the tail a continuous fringe, or are merely separated by the projecting ex- 

 tremity of the latter. The skin is either bare, or contains minute rudimental 

 scales. The backward position of the vent is likewise a characteristic feature 

 of the family. More important is the structure of the upper jaw, of which 

 the front portion of the margin is formed by the premaxillse, while the sides 

 are constituted by the maxillae, which are well provided with teeth. Equally 

 important is the circumstance that posteriorly the skull has no connection with 

 the pectoral arch, which is attached solely to the vertebrae of the neck. Of 

 the soft parts, it will suffice to state that there are no ducts to the reproduc- 

 tive organs. Whereas some members of the family are exclusively marine, 

 others pass a considerable portion of their existence in fresh waters. Among 

 the former are the brightly-coloured and frequently gigantic species constit- 

 uting the genus Murcena, some of which grow to fully eight feet in length. 

 They have no paired fins, although the median ones are well developed ; and 

 save for the presence of the latter, are exceedingly like large snakes. In all 

 the skin is naked, and in many the teeth are very large and powerful. A 

 peculiar feature is the presence of two pairs of external nostrils, of which the 

 foremost are tubular, while the hinder pair are also of a similar type in certain 



