350 
Conspectus of the Species. 
A. The anal plate has four long branches in the same plane, and 
the inner pair is longer than the outer. The anterior ventral 
setæ on the anal segment at least moderatelv long. The last 
pair of legs is long or rather long. 
a. Most of the hairs on the upper surface of the head are 
strongly clavate. No process on the sternum of the anal 
segment. The anal plate is incised almost to the base. 
«. The inner branches of the anal plate without any transverse 
division. European species. 1. P. Huxleyi Lubb. 
ft. The inner branches of the anal plate sharply divided by 
a transverse suture into two parts. American forms, 
f. The lower antennal branch with its posterior fla- 
gellum more than twice as long as the anterior; 
the globulus is very small, its transverse diameter 
conspicuously shorter than that of the upper branch. 
The basal part of the inner branches of the anal 
plate is narrow, the distal part is a round or oval 
knot. 2. P. robustus n. sp. 
ff. The lower antennal branch with its posterior fla- 
gellum only a little longer than the anterior; the 
globulus is moderately large, its transverse diameter 
as long as that of the upper branch. The basal 
part of the inner branches of the anal plate is nar¬ 
row, cylindrical; the distal part is half as long as 
the basal one, thin, linear. 
3. P. intermedius n. sp. 
tf*}-. The lower antennal branch with its posterior fla- 
gellum only a little longer than the anterior; the 
globulus is small, with the diameter conspicuously 
shorter than that of the upper branch. The basal 
part of the inner branches of the anal plate is shaped 
as an oblong disk, much tapering towards the end; 
