920 FISHES — APHEEDODERIDiE. 



lateral line ; vent always anterior ; iia position varying with age, being behind the ven- 

 trals in the yonng and jagular in the adnlt, a singnlar fact, first noted by Prof. S. A. 

 Forbes. A single species in this remarkable family is known. This inhabits the low- 

 land waters, ditches and bayons of the Mississippi Valley and Atlantic coast. 



Gbnus 60. APHREDODERUS. Le Snenr. 



Aphredoderus, LeSnenr, Cuv. et Val., Hist. Nat. des Poiss, ix, 1838, 329. 

 Sternotremia, Nelson, Bull. Ills. Soo. Nat. Hist., i, 1876, 39. 

 Aiiernotremia, Nelson, Jordan, Boll. U. 8. Nat. Mas., x, 1877, — . 

 Aphrodedirue, Cope. Aphododerug, Jordan, corrected orthography. 



Type, Apliredoderus gibboeus, LeSueur, = Scoloptis tayanua, Gilliams. 



Etymology, aphodos, excrement ; dere, the neck or throat, from position of the vent. 



Characters' of the genus included above. The body in the known species is rather 

 short, compressed, thickened and bluutish forward-; the general color is olivaceous, and 

 a dark bar is present below the eye and at the base of the caudal fin. 



The study of the position of the vent, in this genus has 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 geijus 

 Sternotremia was proposed, nor is it apparently an individual or a sexual Character as 

 has since been suggested. The observations of Professor Forbes, verified by myself, ap- 

 pear to show that the position of the vent is dependent on the age of the fish. In the 

 adultj the vent is jagular, close behind the little projaoting 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 pro- 

 portionate to the size of the fish. 



Occasional irregularities occur, but the above rule holds so generally that it cannot 

 be merely accidental. From it, I infer that in the very young, the position of the vent 

 will be found to be as usual in Percoid fishes, as in the young Flounder the eyes 

 are symmetrical, the aberrant characters being developed with age. 



This moving forward of the vent seems to be simply due to the lengthening of the 

 horizontal part of the intestine or " rectum" of the fish. ApJiododerua sayanua is one of 

 the most highly interesting of our fishes and a complete study of its embryology would 

 be very desirable. 



A closely related family Elassomatidw, with a single known species Elassoma zonatum 

 occurs in the streams and ponds of Southern Illinois and may be found in Ohio. It is 

 perhaps the smallest of all spinous fishes. In Elassoma, the vent is normal in position 

 and the ventral rays are in the normal number I, 5. The dorsal fin is reduced in size as 

 in Aphredoderus. 



112. Aphredoderus sayanus (Gilliams) Dekay. 



Pirate Perch. 



Scolopsis sayanus, Gilliams, Journ. Aoad. Nat. Sci. Phila., iv, 182-, 81. j^ 



Aphredoderus sayanus, DeKay, New York Fauna, Fishes, 1842, 35. — Baird, Ninth Smith- 

 sonian Rept., 1855, 326. — Gunther, Cat. Fishes Brit. Mus., i, 271, and of authors 

 generally. 



