GILBERT AND STARKS — FISHES OF PANAMA BAY 165 



304. Prionotus ruscarius sp. iiov. 



Plate XXVII, Fu:s. 50, 50a. 



Pn'ono/its /lorrciis ]oRD.\T<, 1895/;, p. 492 (Mazatlan); Jordan tSc Evermann, 1898, p. 2172 

 (Panama; Magdalcna Bay); nut Prionotus horrcns Richardson. 



Prionotus birostratns ]ov.\> AN, 1885, p. 387; Jordan & Hughes, 1886, pp. 332, 337; not Prionotus 

 birostratus Richardson. 



This species strongly rcseniblos P. horrens, witli which it is found associated. 

 It differs in the coarsely granular head, which is usually strongly hirostrate, the con- 

 cave iuterorbital space, the strongly ctenoid scales, the more numerous rays in the 

 vertical fins, and in the shape of the pectoral. 



Like P. horreiis, this species has a ridge extending from edge of preorbital 

 backward to base of preopercular spine. The ridge is less sharp than in horrens, 

 being scarcely keel-like in our younger specimens, and decidedly rounded in a large 

 individual 34 cm. long. The rostral plates are usually produced into rounded lobes, 

 with a deep emargination between them; but the lobes vary greatly. Where the 

 lobes are large, the preraaxillaries are wholly or almost wholly concealed, when 

 viewed from above. In the largest specimen the lobes project but little, and the 

 premaxillaries are exposed. 



The ridges and granules are much coarser than in P. horrens, more nearly 

 resembling P. tribuliis. The ridges are everywhere easily discernible. The spines 

 are slightly smaller than in P. horrens, but occupy the same positions and are for the 

 most part similarly developed. The supraocular spines are usually smaller, with two 

 present above each orbit, a minute one projecting into a notch in the immediate bony 

 rim of the orbit, and a larger one farther removed from the rim, on the rounded 

 supraocular ridge. But one supraocular spine is present in /''. horrens. The humeral, 

 opercular and occipital spines and ridges are sharper and stronger in P. ruscarius. 



Head 2i to 2| in length to base of caudal; depth 4| to 4|; snout 2j^ to 2 J in head (to edge 

 of opercular flap); eye 5J to 6; interorbital width 4 to 4^. Dorsal X, 12; anal 11. 



Iuterorbital space deeply concave, as in P. tribulus. Anterior nostril with a slender flap, 

 longer than in P. horrens, reaching when depressed to or beyond anterior margin of nostril. The 

 maxillary usually fails to reach vertical from spine on middle of cheek. The intermandibular space 

 is rounded anteriorly; there is little or no trace of a symphysial knob. Vomerine patch of teeth con- 

 stricted mesially in young specimens, wholly divided into two separate patches in adults. Each half 

 of vomerine patch about equals one of the palatine bands. Gill-rakers 6 (movable), the longest about 

 three-fourths diameter of pupil. The membrane between the opercular spines is covered with cycloid 

 scales. 



Scales thick and firm, strongly ctenoid on back and sides, becoming cycloid. on belly and 

 breast, and on anterior portion of nape. The scales of the lateral line are le.ss roughened than in 

 P. horrens, the edges not strongly spinous. The breast is almost completely scaled, a small tract 

 immediately behind the isthmus, and a narrow area at base of each ventral, naked. There are 50 to 52 

 scales in the lateral line, and about 100 vertical series above the lateral line. 



The dorsal spines are flexible, but stronger than in P. horreiis. The first and second spines 

 are about equal, the succeeding ones rapidly shortened, the margin of the fin straight. The ninth 

 spine bears a movable membrane. The tenth is immovably imbedded, very strong, the basal tubercle 



(S2) December 29, 1903. 



