786 Bulletin ^7, United States National Museum. 



spines, which are rapidly graduated, the first being very short. Anal 

 small, with two slender spines ; ventral fins thoracic, with a very short 

 spine, the number of soft rays usually 7 ; caudal fin rounded behind. 

 Air bladder simple, large, adherent to the walls of the abdomen. Verte- 

 brae 14 + 15. Pyloric cceca about 12. A single genus, with probably but 

 one species, confined to the United States. Its relations are most close to 

 Cohimhia and Percopsis among living fishes, but it differs strikingly from 

 these in the loss of the archaic characters of the adipose fin and the 

 abdominal ventrals. The position of the vent is not seen in any closely 

 related group, but reappears in the Amhlyopsida', likewise an ancient type 

 without close relationships among living fishes. {Aphredoderidw, GUnther, 

 Cat., I, 271, 1859.) 



351. APHREDODERUS, Le Sueur. 

 (Pirate Perches.) 



Aphredodeni^, Lb Sueur, in Cuvier& Valenciennes, Hist. Nat. Poiss., ix, 445, 1823, (gihbosiis=: say- 

 anus). 



Steitiotreniia, Nelson, Bull. Ills. Lab. Nat. Hist., i, 39, 1876, {isolepk). 



.ds^cnioh-ewM (Nelson) JoRiiAN, Bull. U. S. Nat. Mus. , x, 52, 1877, {holepis; Sternotremia being 

 regarded as anatomically incorrect). 



Characters of the genus included above. (d<po6o(:, excrement; (Uy*?;, the 

 throat, from the position of the vent; hence more correctly ^j>/iorfofZerMs.) 



1147. APHREDODERUS SAIANUS (Gilliams). 

 (Pirate Perch.) 



Head 3; depth 3. D. Ill, 11 to IV, 10; A. II, 6; V. 7; B. (5; scales 45 

 to 60. Color dark olive, profusely speckled with dark i>oints, which often 

 make blackish streaks along rows of scales ; 2 blackish bars at base of 

 caudal, between which is a light bar. Length 5 inches. Sluggish streams 

 and bayous from New York coastwise to Texas, and throughout the Mis- 

 sissippi basin in lowlands and streams with alluvial bottoms; locally 

 abundant, variable. The singular variations in the position of the vent 

 have given rise to two nominal species and a nominal genus.* North- 

 western specimens, Ohio to Arkansas (var. isolepis) have usually 

 smaller scales than the true sayanua. Sayanus has 45 to 55 ; isolepis usually 

 55 to 60; both forms are extremely variable and probably no constant dif- 

 ferences exist. (Named for Thomas Say, the distinguished entomologist.) 



* "A study of the position of the vent in Aphododentssaiiamis'ha.a developed some singular things. 

 It becomes evident from the examination of a large series that the position of the vent is not a 

 character of generic importance, as was supposed when the genus Sternotreniia was proposed, nor 

 is it apparently an individual or a sexual character as has been since suggested. The observa- 

 tions of Professor Forbes, verified by myself, appear to show that the position of the vent is 

 dependent on the age of the fish. In the adult the vont is jugular, close behind the little pro- 

 jecting knob at the throat. In the youngest specimens examined, it is more or less behind the 

 ventral fins. In specimens intermediate in size, its position is intermediate, the degree of 

 advancement being proportionate to the size of the fi.ih. 



" Occasional irregularities occur, but the above rule holdf so generally that it can not be merely 

 accidental. From it I infer that in the very young the position of the vent will be found to be 



