2032 Bulletin ^7, United States National Museum, 



of plates of Agonus, etc. In the following descriptions of species, when 

 the diameter of the eye is not specified, the longitudinal diameter is meant. 

 The rays of the fins arise regularly in the intervals between the successive 

 pairs of plates alternating with them, and the membrane behind the last 

 spine of the first dorsal fin ends at variable distances from the base of the 

 spine; hence in giving the number of plates between the dorsals, the num- 

 ber between the last spine and the first ray is meant, unless otherwise 

 stated. " Length of body," as the standard of measurement, means the 

 length from tip of premaxillary to base of caudal, unless " total length " 

 is mentioned. The rostral spines, whether 1 or 2 pairs, belong to the nasal 

 bones, and are properly "nasal spines" in the species in which there is no 

 free terminal plate. The latter, with its spines, may be the freed anterior 

 part of the nasal bones. The hypural bone is included in the number of 

 vertebrae, and these were counted in nearly all cases in only 1 individual. 

 The young of several species have been described, some of them in detail, 

 and so far as known they all differ from the adults in the same way. The 

 spines and ridges are more prominent; the body is relatively shorter, its 

 anterior end abruptly broader, forming with the head a more or less defi- 

 nite rhombic figure ; the tail is more compressed ; the head is broader, the 

 snout more blunt, and the lower jaw relatively longer; the vent lies far- 

 ther back from the base of the ventral fins, and there are usually pairs of 

 small plates between them; the dorsal and ventral series of plates on the 

 tail, which are single in the adults of nearly all the species, are double in 

 the young, or at least have the double row of serrations. Nearly all the 

 species are found within the limits assigned to this work. The few not so 

 found are included, for completeness' sake, in footnotes. (F. C.) 



a. Spinous dorsal present. 



b. Gill membranes free from the isthmus. 

 PERCIDINJE : 

 c. Body compressed; lower jaw not projecting; plates of body spinous; first 



dorsal at nape. 

 d. Body elongate; dorsals well separated. 



e. Teeth on vomer; no occipital spines or barbel on snout. 



PERCIS, 759. 



ee. No'teeth on vomer ; snout with a long barbel ; occipital spines present. 



AGONOMALUS, 760. 



dd. Body short and high; dorsals close together; vomer without teeth; 

 occipital spines present; lower rays of pectorals free. 



HYPSAGONUS, 761, 

 BRACHYOPSINJS : 

 cc. Body more or less depressed; lower jaw projecting; plates of body spinous 



or not; first dorsal behind nape. 

 /. Chin without terminal barbel. 



g. Snout short (not produced in form of a tube) ; plates of body spinous. 

 h. Bones of snout short, not forming a tubular nose. 



i. Vomer and palatines without teeth ; breast simply prickly. 



STELLERINA, 762. 



u. Vomer and palatines with some teeth ; breast with large 



plates. OCCA, 763. 



hh. Bones of snout produced into a long tube which bears the short 



jaws at the end ; body rather robust, the plates with spines. 



BRACHYOPSIS, 764. 



