PERCESOCES 



641 



scales. Eibs attached to the extremity of strong parapophyses. 

 rectoral fin inserted low down, with a lower portion consisting of 

 free rays ; the upper portion, or fin proper, attached to the 

 scapula, the lower to a fenestrate bone which appears to be 

 formed by coalesced pterygials (Fig. 391, pt?). Ventral fin more 

 or less approximated to the pectoral, with one spine and five soft 

 rays ; pelvic bones suspended from the post-clavicles. Two well- 

 separated dorsal fins, the anterior formed of a small number of 

 spines. Air-bladder, if present, very large. 

 The vertebrae number 24 (10 -|- 14). 



Fig. 392. — Polynemus quadrifiUs, x J. (After Cnvier and Valenciennes.; 



Three closely allied genera : Polynemus, Pentanemus, and 

 Galeoides, with about 2 species, from the shores of tropical seas, 

 often entering rivers. Some attain a length of 4 feet, and are 

 valued as food or for the isinglass yielded by their air-bladder. 

 The free pectoral filaments are organs of touch, and can be moved 

 independently of the fins. 



Fam. 6. CMasmodontidae. — The deep-sea genera, Chias- 

 viodon, Pseudoscopelus, and Champsodon, which have been placed 

 either with the Gadidae, the Trachinidae, or the Berycidae, may 

 be referred to the Percesoces, as the pelvic fins have only a 

 ligamentous connexion with the pectoral arch. Unfortunately, 

 the skeleton has only been examined in Champsodon ; it is 

 remarkably similar to that of the Atherinidae. As in Atherin- 

 ichthys, the posterior extremity of the air-bladder is protected by 

 a bony sheath foi-med by the expanded ring-like haemal processes 

 of the anterior caudal vertebrae. Vertebrae 32 (164-16). The 



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