GILBERT AND STAKES — FISHES OF PANAMA BAY 163 



The head is very finely granular, the radiating ridges delicate and very numerous, the minute 

 granules almost uniformly covering the bones. The anterior margin of the preorbitals is minutely 

 serrulate or i,>-ranular, the posterior tooth sometimes larger than the others, projecting spine-like. 

 Immetlialely behind the rounded portion of the preorbital, from which it is separated by a notch, is a 

 strong compressed spine directed outward and backward. Behind this, on the ridge already mentioned, 

 is a series of similar spines increasing in size posteriorly. One of those is on the center of the pre- 

 orbital, one on the center of the cheek, the thirtl at the base of the preopercular spine. These spines 

 decrease but little with age; but it may be possible that none of our specimens is fully grown. The 

 preocular, supraocular, occipital, nuchal, opercular and humeral ridges and spines offer nothing 

 peculiar. No spines immediately behind the eye. A single pair, similar to the occipital spines, 

 located slightly in advance of the latter, on the blunt postocular ridge. No trace of a jxistocular 

 groove. 



The anterior nostril has a broad short flap arising from its posterior margin. Mouth large, 

 the ma.xillary reaching a vertical which passes through spine on middle of cheek and traverses the 

 orbit midway between its anterior margin and the front of the pupil. Mandible with a small but 

 evident symphysial knob, much better developed than in P. ruscarius, the intermandibular space 

 anteriorly acute. Vomerine and palatine patches of teeth varying greatly in width, the vomerine patch 

 greatly constricted mesially, but not wholly divided in any of our specimens. The vomerine patch 

 about equals in length one of the palatine patches. Gill-rakers varying in length from two-fifths to 

 four-fifths diameter of pupil. They are usually heavy, club-shaped; 6, or rarely but 5 movable ones 

 are developed on horizontal limb of arch. The membrane between the op)ercular spines is partly cov- 

 ered with cycloid scales. 



Scales thin, smooth or weakly ctenoid in the young, wholly smooth with entire edges in 

 adults. The scales of the lateral line have their exposed portions roughened with minute projections, the 

 free edges coarsely spinous in the young. The size and roughness of these scales vary widely in 

 different individuals. The sides of body are wholly scaled, save for a narrow naked strip in the a.xil 

 of the pectorals and ventrals. The breast is variously scaled, but less completely so than in P. 

 ruscarius. The scaled tract is sometinies limited to a narrow medial band, with a constriction opposite 

 the base of the \entrals; when wider than this, it is in adults still bounded in front and on the sides 

 with distinct naked margins. There are 52 scales in the lateral line, and about 100 vertical series 

 above the lateral line. 



The dorsal spines are slender and flexible, none of them roughened or serrulate on their 

 anterior margin. The first spine is but little shorter than the second (the longest) ; the free margin of 

 the fin is slightly concave. The eighth is the last spine to bear movable membrane, the ninth being 

 thick and short, declined, firmly embedded in the integument, and the tenth little more than a conical 

 bony nodule, which is sometimes entirely concealed. The caudal is truncate when spread, rarely 

 slightly emarginate. The pectorals are very short, barely reaching the vent in adults, slightly beyond 

 that point in the young. In the very immature type (115 mm. long), the pectoral is figured as e.xtend- 

 ing to a point opposite the fourth anal ray. The posterior margin of the fin is evenly rounded, the sixth 

 to the eleventh rays the longest. Detached pectoral rays very long and slender, the uppermost about 

 as long as the rest of the fin, e.xtending well beyond tips of ventrals. In adults, the tips of ventrals 

 fall a little short of the tips of the pectorals, and neither fin reaches the vent. 



The dorsal contains invariably 10 spines and 11 soft rays; the anal has but 9 rays. As noted 

 above, the last dorsal spine (or tubercle) is sometimes concealed. 



Color in spirits : dusky brown above, an obscure broad dark bar extending downwards from 

 anterior part of spinous dorsal, and a second, more distinct, from posterior part of soft dorsal. A 

 dusky shade on cheeks, continued on to lower side of head, where it widens from the cheek spine 

 backward to behind tip of maxillary. Lower parts bright white. Spinous dorsal dusky, especially on 

 its anterior half, where there may be disconnected traces of a distinct black margin. Gill-cavity 

 blackish; peritoneum white. 



