XXII PERCESOCES 641 
seales. Ribs attached to the extremity of strong parapophyses. 
Pectoral 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, pé.). 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). 
K< ‘2 
aaiiad as 
te SO CRO = 
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XX) OV ONS , = 
Fic. 392.—Polynemus quadrifilis, x4. (After Cuvier and Valenciennes.) 
Three closely allied genera: Polynemus, Pentanemus, and 
Galeoides, with about 25 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. Chiasmodontidae.—The deep-sea genera, Chias- 
modon, 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 formed by the expanded ring-like haemal processes 
of the anterior caudal vertebrae. Vertebrae 32 (16+ 16). The 
VOL. VIT Bee 
