THE AMERICAN NA TURALIST. [Vol. XXXV 1 1 . 



All the specimens are from Boynton's Pond, a shallow sheet of 

 water about one hundred feet in diameter on the outskirts of 

 Passaic, N.J. 



Habrophlebia americana Banks mss. 

 This fine little species was common among the floating 

 masses of Spirogyra which skirt the edges of the pond ; rather 

 sedentary in habit, but very active swimmers when disturbed. 

 They swim by rapid vertical movements of the abdomen, mean- 

 while holding it considerably elevated. The chief organs of 

 locomotion are the flattened abdomen with the expanded lateral 

 margins of its segments. The caudal setae are weak and but 

 thinly clothed with hairs, and can be of but little assistance in 



swimming. The abdomen is not held in a raised position when 

 the nymphs are resting, as it is in Callibaetis, for instance. 



Antennae slender, about 2 mm. long, sparsely and minutely 

 hairy at the joints toward the base. Head wider than long, 

 with the eyes on the posterior lateral angles. Color dark 

 brown ; margins of the abdominal segments and their lateral 

 extensions, together with the terminal third of the caudal seta?, 

 yellowish. Abdomen flattened ; segments 3 to 6 about the 

 same width and becoming slightly longer; segments 7, 8, and 

 9 rapidly narrowing, the ninth being about half the width of 

 the third; posterior margins of segments 6 to 10 minutely 

 toothed ; lateral margins of all the segments produced more or 

 less beneath the gills, thus protecting them when swimming. 

 This lateral expansion increases posteriorly, and the posterior 

 lateral angles of segments 8 and 9 are produced into a sharp 

 spur. 



