PERCESOCES / 



h'. Vertebrae more than 30; anal fin with a single spine (3 in Nannatherina) ; 

 head sharp ; "lower limb of post-temporal attached to opisthotic by liga- 

 ment; basisphenoid developed; myodome opening to exterior posteriorly; 

 region about foramen magnum not produced ; superior pharyngeals typical 

 in shape, bearing teeth" (Starks, /. c.) Atherinid^ 



It is evident from the foregoing analysis that each of the three 

 famiHes possesses certain primitive traits, and that each is highly modi- 

 fied in its own direction. 



The Percesoces have usually been defined as teleost fishes with 

 cycloid scales, a spinous dorsal, and with ventral fins composed of a 

 spine and five soft rays, subabdominal in position. A view of their 

 relationships which has long remained in favor was expressed by Jordan 

 and Evermann* in these words : "The suborder marks a transition from 

 soft-rayed to spiny-rayed fishes, its nearest relatives among the latter 

 being, perhaps, the Scombroid forms." Professor E. C. Starks, in a 

 paper on "The Osteological Characters of the Fishes of the suborder 

 Percesoces/"* wrote : 



"In examining the crania of these species attention is attracted at 

 once to the fact that in all of them the epiotics are developed into long. 

 thin processes which divide into more or less bristle-like filaments. 



"There is little else in purely internal characters whereby to differ- 

 entiate these families as a group from the other Acanthopteri. In 

 order so to differentiate them we must turn to the well-known external 

 characters — a spinous dorsal in conjunction with the abdominal ventral 

 fins, high pectoral fins and unarmed opercles." 



The taxonomic value of these minor differences may be questioned, 

 inasmuch as the Percesoces are so like the typical percoid fishes in 

 general structure. Unarmed opercles, not being rare in the Percoidea, 

 offer no substantial character upon which to define the group. Similarly 

 the scales of many percoids, having lost their armature, are secondarily 

 cycloid; in some of these cases, as in certain Embiotocid^, the finer 

 structure of the scale is closely similar to that of the Percesoces: con- 

 sequently the scales of this group may have developed from a typical 

 ctenoid type. The pectoral bases, especially in the Mugilid.e and Ather- 

 INID^, are higher and more oblique than in typical perch-like fishes, 

 but in one genus of the Atherinid.e, Nannatherina, the pectorals are 

 "Symmetrical, rounded, placed rather low (as in normal Perciform fishes 

 rather than as in other Atherinids)."® The flexibihty of the dorsal 

 spines in the Percesoces, and their separation from the soft rays as a 

 distinct fin, are characters paralleled in several groups of obviously per- 



*Biill. U. S. Nat. Mus., 47, pt. 1, 788, 1896. 



'^Proc. U. S. Nat. Mus., 22, 1-10, pis. 1-3, 1900 (Oct. 7. 1899). 



« Regan, Ann. Mag. Nat. Hist. (7). 18, 451. 1906. 



