190 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
* Daphina exilis sp. n.? 
PLATE LII, Fias. 4, 5. 
It is admittedly undesirable to describe a specimen instead of a 
species, but the form for which the above name is provisionally pro- 
posed is so peculiar and its locality so little studied that a description 
is given based ona single young female. It will be understood that 
the ovigerous female would differ in the length and position of the 
Spine, size of crest and form of the abdominal processes. 
A daphnid of moderate size with crested head, long spine and den- 
tate caudal claw. Nearly colorless. Head projecting in the line of 
the axis of the body, crested from the eye to a point cephalad of the 
heart, but truncate in front. Ventral outline nearly straight, beak 
not projecting, antennules very short and applied almost at the end 
of the beak, which does not lie between the valves. Eye of rather 
large size, with few crystallines, near the ventral margin. Pigment: 
fleck small, nearer to the caudal margin of the head than to the eye. 
Cceca narrow, strongly curved. Antenne short and stout, second 
segment of the setze longer than the basal. Fornix moderate. Valves 
sub-oval, strongly curved ventrally, dorsal outline straight from in 
front of the heart to the spine, which is very long and curved dorsad. 
In this specimen the spine is longer than the entire valve. There is 
no dorsal emargination between the head and body. Dorsal margin 
armed with spines beyond the heart, ventral margin spined more than 
half of the length. Valves marked with the usual quadrangular 
meshes. Post-abdomen narrowed toward the end. Anal margin sin- 
uate. Anal teeth about eight, nearly equal. Claw short and moder- 
ately curved, armed with a continuous series of spinules and a comb 
of fine spines near the base. Length, exclusive of spine, 1.15 mm.; 
length of head 0.38 mm., height of head 0.54 mm., height of shell 0.65 
mm., length of spine 0.84 mm., diameter of eye 0.10 mm, length of 
base of antennze 0.26 mm., claw 0.09 mm, The abdominal processes 
in this specimen are not in their mature form. It is not certain that - 
the dense hairiness of the anal margin above the teeth is an adult 
character. It would appear that the crest is normally a strongly pro- 
jecting cephalic helmet, but this is but conjectural. Found in weedy 
pools fed by irrigation canals at Albuquerque. 
* Daphnia arcuata Forbes. 
Forbes ’93. 
‘‘Head helmeted, rounded in front, length one-third that of the 
shell, front concave, beak produced, extending beyond the sensory 
hairs of the antennee. Eye small, about midway between the mandi- 
pends 
