EDWIN CHAPIN STARKS 33 



abruptly at the beginning of the fine soft part of the barbel. The groove 

 that it occupies encroaches somewhat upon the eyeball below. There is only 

 about one of these specimens to a dozen of the others. 



Between these extremes are nearly all of the intermediate stages, and 

 coordinating with it are the size and shape of the first anal rays. These 

 are enlarged and form a process in the specimens with the large, bony, 

 curved maxillary barbel, but not at all differentiated from the other rays 

 in those with the straight, fine, scarcely ossified barbel, while they are 

 slightly enlarged in those with the barbel slightly enlarged, curved and 

 ossified. 



The enlarged anal process suggests a copulatory organ. It is as long 

 as the pectoral spine, or two-fifths longer than the rays behind it, and is 

 formed of two rays, with a third slightly enlarged and closely attached to 

 it. These appear to be the first rays, but upon dissecting away the integu- 

 ment two slender shorter rays are found in front of them. The enlarged 

 rays, though they become stiff and spine-like, do not lose their articulations. 

 The tip of the process is strongly hooked up and back. In a specimen with 

 the ossified portion of the barbel no wider than the pectoral spine, and the 

 ossified portion shorter and passing into the fleshy portion imperceptibly, 

 the anal process is enlarged but not hard and spine-like at the tip, and not 

 hooked up. In those where the condition of the barbel is about midway 

 between the extremes, that of the anal process is also about midway between, 

 perceptibly enlarged, but not longer than the other rays. 



Whether these characters go with sex I am unable to ascertain with 

 the specimens at hand. Some specimens have the abdominal cavity filled 

 with fat, and the bases of the fins thickened with fat. This gives to the 

 fins of preserved specimens an orange-yellow color. In other specimens this 

 condition is not apparent. It cannot be correlated with the condition of the 

 barbel or anal process. 



105. Ageneiosus ucayalensis Castelnau. 



Many specimens were taken in the market at Para, where it seems to 

 be as abundant as Ageneiosus dentatus, which it much resembles. From the 

 latter it may be known by the slightly more slender body, the longer snout 

 as compared with the width of the head at the eyes (as compared with the 

 length of the head or the body the difference does not appear), the smaller 

 eyes, the wider band of teeth on the premaxillary, the longer and more 

 strongly curved mouth, the more strongly projecting upper jaw, and the 

 slenderer spines. The color is usually more bluish, less spotted above, be- 

 coming more abruptly white on the sides, and seldom with a black or dusky 



