64 



occasionally but little more than half the size of the average; 

 the largest female observed in the entire material was 20.5 mm. 

 long and 0.6 mm. in diameter; the largest male observed, 

 12 mm. long and 0.35 mm. in diameter. The largest examples 

 were found in the conures and in the Senegal parrot. The 

 worms are of filarial shape (Fig. 1), long and slender, cylin- 

 drical in section, rigid and colorless. Thickest level of 

 females at about two thirds of length from head; of males, 

 near middle of body length. From these levels the speci- 

 mens taper anteriorly in delicate manner to the head end, 

 which at base of lips in a female of 12 mm. length measured 

 0.08 mm. in diameter (0.06 mm. in male somewhat over 8 mm. 

 in length). Posteriorly the females taper uniformly and 

 finely to an acutely conical straight tail (Fig. 6), with the tip 

 slightly inclined dorsally; the tail of the male a little less 

 acutely conical and curled ventrally. Cuticle finely striated 

 transversely, transparent; and on each side at the head end 

 the cuticle is raised into an uncertain and asymmetrical 

 expansion (Fig. 2) with crenulated margin (in the female 

 used for measurements reaching 1 mm. backward from head 

 on one side and less than half this distance on the other). 

 The head (Figs. 4 and 5) is small and is provided with six 

 lips. Of these, two are large, thick lateral lips (Fig. 4, a), 

 with broad and nearly straight anterior border, the sides 

 incurved and the base about half the length of the anterior 

 free border. These lips are armed with three prominent 

 conical teeth on the anterior border; on their external sur- 

 face, from base to anterior border, extends a depressed median 

 line, on each side of which the lip substance rises in a rounded 

 elevation. Midway between the free border and base on the 

 external surface is a horizontal row of three small and easily 

 overlooked papillae. On either side of these lateral teeth is a 

 smaller submedian lip (Fig. 4, b and c) with rounded margin 

 and broad base, unarmed. Dorsally and ventrally between 

 the two adjacent submedian lips is a sharp-edged prominence 

 projecting into the oral cavity (Fig. 4, e and /) looking from 



