Pomona College, Claremont, California Hl 
branchi# in a simple series; seventeen pairs. Collar well developed, produced for- 
ward below in two pointed lobes overlapping at the middle. Eight setigerous tho- 
racic somites. Most dorsal thoracic sete in each fascicle long and finely pointed with 
wings narrow; the ventral sete much more numerous, shorter, spatulate, with fine tip. 
The uncini have the posterior process very short, rounded at the end, much shorter 
and more slender than the neck, which is rather strongly curved; vertex high and 
narrowly rounded; beak not strongly depressed. Type incomplete, only seven of the 
abdominal segments being present. 
Length of first sixteen segments, 15 mm.; including branchiz, 21 mm.; width, 
2.5 mm. 
Type—M. C. Z. 2, 172. 
Potamilla colorata sp. nov. 
The type is notably marked with black pigment; the collar membrane crossed with 
a close series of longitudinal dark stripes, one in line with each radiole and nar- 
rowing caudad; the branchie crossed transversely with dark bands. Thoracic somites, 
more notably the anterior ones, with a dusky to black band in front of each uncini- 
gerous torus and a dark spot on the dorsum mesad of the setigerous papilla. The 
collar with a dark area ventrad and also dorsad of the fascicles Ground color 
greyish of light brown cast, lacking the yellow dominating in omissa. Sixteen (or 
seventeen) pairs of radioles in the branchie. Ventral lobes of collar pointed, widely 
overlapping in the median line, dorsal ends free, projecting toward each other in 
dorsal groove. Setigerous thoracic somites eight in number. Inferior sete numerous, 
spatulate, usually in two series. Total number of segments present about fifty-one, 
a few of the most caudal being lost. 
Length, 25 mm.; with branchiz, 30 mm. 
Type—M. C. Z. 2,173. 
Pseudopotamilla paurops sp. nov. 
A rather slender species with branchi# of moderate length. Excepting the eyes 
with no pigmented markings. Radioles fifteen pairs. Eyes few, not present on all 
radioles; where present usually but a single one on each radiole, in one case two; 
the eyes deep purple, variable in side from moderate to small; situated at varying 
distance between base and middle of length of radioles. Free dorsal edge of branchial 
membrane with two short obtuse lobes overlapping in the middle line. The dorsal 
notch in the collar lobe on each side is mesad of the line of setigerous tubercles, wide 
open, rectangular or slightly obtuse; lobe mesad of notch small, anteriorly rounded, 
the mesal edge extending into the dorsal furrow; median ventral lobes separated by a 
narrow incision, short, the ectal edge passing out in an even concave curve to the 
anterior lateral margin. A characteristic feature of the species is the presence of ten 
setigerous thoracic somites. Dorsal sete of the usual two types of which the upper 
are much fewer spatulate sete in two series with distal expansion broad and wings 
asymmetrical, tip short. Total number of segments, seventy-eight. 
Length without branchiz, 31 mm.; with branchie, 36 mm. 
Type—M. C. Z. 2, 174. 
Tube tough, corneus. 
Pseudopotamilla parva sp. nov. 
The type of this species is a small individual which, as preserved, appears of a 
uniform dusky color throughout. Branchial radioles fourteen or fifteen pairs; in a 
