A NEW FRESH-WATER CRUSTACEAN. 29 
ing, white, mottled with brown. Palmar margin of hand 
strongly angulate near the base, the angle preceded by 
about five short spines. Between the angle and the dac- 
ty\ is a large, sharp tooth-like projection. Dactyl with 
minute appressed spines on the inner edge, terminating in 
a small claw. First genital plates of male with the quad- 
rate basal segment about equal in length to the greatest 
width of the lance-shaped distal segment. Second pair of 
genital plates of male with proximal segments about as 
wide as lonoj ; distal segment of outer ramus frino^ed with 
long hairs, obliquely truncate. Caudal appendages of 
adults rather large ; the pedicel slightly excavate at middle 
of its inner margin, about two and a half times as long as 
wide ; outer ramus about three-fourths the length of the 
inner ramus. 
Length of adult males .63 inch ; width .25 inch ; lower 
antennse, .38 inch. Length of adult females .44 inch. 
A large and abundant crustacean in springs and spring- 
fed rivulets and ponds in eastern Kentucky. Large ex- 
amples are of a dull gray color with the expanded lateral 
portions of the head and body- segments paler. In young 
the contrast between the central and lateral portions of 
segments is more decided, and two longitudinal dusky 
bands appear on each side, one just outside of the median 
ridge, and the other just within the expanded lateral por- 
tions of the segments. 
The species is closely related to the Virginian Manca- 
sellus hrachyurus, but may be distinguished at once by the 
fissured lateral portion of the head, and by the greater 
length and different shape of the caudal appendages. Other 
differences equally important with these become appar- 
ent under the microscope, as will be seen by comparing the 
accompanying figures. 
