2280 Bulletin 47, United States National Museum. 



terminal, horizontal, its cleft usually very wide, the maxillary sometimes 

 greatly dilated; supplemental maxillary present; premaxillaries pro- 

 tractile; jaws subequal, with conical or cardiform teeth; vomer usually 

 with a few teeth ; palatines toothless ; opercles unarmed ; no suborbital 

 stay. Pseudobranchiae present. Gill rakers rather long; gills 4, a slit 

 behind the fourth; gill membranes somewhat united, free from the isth- 

 mus. Branchiostegals 6. Air bladder present. No pyloric caeca. Ver- 

 tebrae large, about 27 in number. Dorsal fin long, continuous, its anterior 

 half composed of slender, flexible spines, which pass gradually into soft 

 rays; caudal distinct, rounded or lanceolate; tail not isocercal, the last 

 vertebra expanded (27 to 34) ; anal long and low, without distinct spines; 

 ventrals separate, jugular, I, 5, the middle rays longest; pectorals fan- 

 shaped. Three genera, of about 15 species ; small fishes inhabiting rocky 

 bottoms in tropical seas, many of them with bright markings. The 

 American species are all rarities, living about rocks in deep or shallow 

 water; nowhere abundant and none of the species well represented in col- 

 lections. (Trachinidw, genus Opisthognathua, Giinther, Cat., n, 254-256.) 



a. Maxillary of great length, nearly as long as head, produced behind in a flexible 

 lamina. OPISTHOGNATHUS, 841. 



aa. Maxillary normal, truncate behind, much shorter than head. 



&. Caudal moderate, rounded behind ; body oblong, moderately compressed. 



GNATHYPOPS, 842- 

 &&. Caudal lanceolate, long and pointed ; body elongate. LONCHOPISTHUS, 843. 



841 . OPISTHOGNATHUS, Cuvier. 



Opisthognathus, CUVIER, Regne Auim., Ed. 2, vol. n, 240,1829 (sonnerati). 



Masillary prolonged backward in a long flexible lamina, which reaches 

 about to base of pectoral. Characters of the genus otherwise included 

 above. It has been suggested that the species of Gnathypops are females 

 of analogous species of Opisthognathus, the long maxillary being a charac- 

 ter of the male. This seems impossible, but deserves an investigation. 

 The fact that Gnathypops maxillosa has but 27 vertebrae, while its long- 

 jawed cognate, Opisthognathus macrognathum, is said by Poey to have 34 

 vertebrae, is opposed to this view, as is also the fact that the analogous 

 species do not in other respects exactly correspond, as in Gnathypops mys- 

 tacina, the scales are smaller than in Opisthognathus lonchurum; Gnathypops 

 rhomalea has fewer fin rays than Opisthognathus punctatum, etc. But the 

 parallelism of species in the two genera living in the same waters is 

 remarkable. (6' TtitiQe, behind; yvdQoS, jaw.) 



a. Scales moderate, about 67; D. X, 15; A. II, 13; body nearly plain olivaceous, the 



maxillary not distinctly striped within. LONCHURUM, 2615. 



aa. Scales very small, 100 to 150 in longitudinal series; dorsal rays about XI, 17; A. 



11,16; body and fins much variegated, the maxillary within with 2 ink-black 



stripes on a milk-white ground. 



b. Dorsal without large black spot in front; scales 120. PUNCTATUM, 2616. 



&&. Dorsal with a large black spot more or less ocellated. 



c. Scales about 100. MACROGNATHUM, 2617. 



cc. Scales about 140. OMMATUM, 2618. 



