782 Bulletm 47, United States National Museum. 



Hapi.udoci: Ventrals jugular, with 2 or .'i soft rays; post-temporal undiviiled; gills 3, a slit 

 behind the last ; no suborbital stay; spinous dorsal very short; no pseudobranchiae; tail diphy- 

 cercal. 



Xenopteryoii: Ventrals wide apart, I, 4 or I, 5, a broad sucking disk formed of folds of skin 

 between them; no spinous dorsal; no suborbital ring; no scales; tail diphycercal. 



Blf.nnioiuei: Ventrals jugular, usually with 1 spine; less than 5 soft rays, often wanting; dor- 

 sal fin very long, its anterior portion composed of numerous spines; hypercoracoid perforate; 

 shoulder girdle, jaws, nostrils, and suborbital normal; tail diphycercal; pseudobranchia; present; 

 scales usually small and smooth, often wanting; vertebras numerous. 



Ophidioidei; Ventrals without spines; no spines in the anterior portion of dorsal fin. Other- 

 wise essentially as in the Bhnmoidei, the tail diphycercal, the last vertebrje sometimes much 

 reduced. 



Anacaxthini: Ventrals jugular, of soft rays only, the number usually more or lefs than 5; no 

 spines in any of the fins; hypercoracoid iraiierforate; tail isocercal; no pseudobranchia;; gills, 

 nostrils, pharyngeals, suborbital, and shouldi-r girdle normal; vertebrje numerous. 



Tjeniosomi: Body ribbon-shaped; the ventrals thoracic, the.rays usually less than I, 5; post- 

 temporal undivided; skin smooth or prickly; caudal fln wanting or else divided and peculiar. 

 Skin naked or prickly; vertebra; very numerous. 



Heterosomata: Cranium twisted so that both eyes in the adult are on the same side of the head; 

 dorsal and anal fins very long; no spines in the fins; ventrals thoracic, of more than 5 soft rays; 

 coracoids normally developed, the hypercoracoid perforate; tail diphycercal; pseudobranchise 

 present; vertebra; in increased number. 



Suborder SALMOPERC^. 

 (The Trout Perches.) 



We place provisionally as a sitborder of the Acanthopteri, a singular 

 group of archaic fishes, relics* of some earlier fauna, and apparently 

 derived directly from the extinct transitional forms through which the 

 Haplomi and Acanthopteri have descended from allies of the Isospondi/li. 

 The group shows the remarkal)le combination of true fln spines, ctenoid 

 scales, and a percoid mouth, with the adipose fin, abdominal ventrals, and 

 naked head of the Isospondyli. The relations of the PercojJsidce with 

 such archaic spiny-rayed fishes as Apliredoderus and Elassoma are cer- 

 tainly not remote and the close resemblance of the head of Fercopsis to 

 that of Gymnocepkaliis {Acerina) may be more than accidental. The sub- 

 order may bo provisionally defined as follows : 



Ventrals abdominal, each with a short simple ray ; dorsal with 2 sim- 

 ple rays or spines ; anal with 1 or 2 ; mouth formed as in Percoid fishes, 

 the simple toothless maxillary not forming part of its border. Adipose 

 fin present. Scales ctenoid ; head naked ; pseudobranchia} present. Air 

 bladder apparently with a rudimentary duct. Stomach siphonal, with a 

 few ccEca. Shoulder girdle without mesocoracoid, apparently of the 

 normal percoid type ; vertebra- about 35. A single family. (Salvia, tvout; 

 Perca, perch.) 



* In describing Perccypmn, Agassiz refers to it as a generalized type and relic of an older fauna. 

 He says: "Now, the genus Percopsix is as important to the >inderstanding of modern types as 

 Lc'pidiisleus and Cestraciou are to the understanding of the ancient ones, as it combines charac- 

 ters which in our day are never found together in the same family of fishes, but whicli, in 

 more recent geological ages, constitute a striking peculiarity of the whole class. My Percopsis 

 is really such an old-fashioned fish, as it shows peculiarities which occur simultaneously in the 

 fcssil fishes of the Chalk epoch, which, however, soon diverge into distinct families in the Ter- 

 tiary period never to be combined again. Now my new genus Percopsis is a just intermediate 

 between ClenoUh and Ci/doids; it is what an ichthyologist at present would scarcely think 

 possible, a true intermediate typo between Percoids and Salmonida;." (Agassiz, Lake Superior, 

 285, 1850.) 



