PACKAND.] PHYLLOPODS OF NORTH AMERICA. 325 
Total length of carapace, 19™™; width of the same, 17™™. 
Length of keel on the carapace, 84~™; from anterior end of keel to 
front edge of carapace, 6™". 
Length of abdomen beyond the carapace, 213". 
Length of caudal appendages, 20". 
Diameter of the ovisaes, 257". 
Our female differs from the males in the carapace being longer, with 
28 segments, uncovered, beyond the carapace; and 10 segments bevond 
that bearing the last pair of appendages, while the under side of the 
telson is much smoother than in the males, but the upper side as in the 
males; the caudal appendages less spiny than in the males. 
The ovisaes contained a few eggs, which were of the same size as in 
A. lucasanus and otherwise the same, except that the germ had com- 
menced to develop; they were arranged in the cavity of the ovisac side 
by side in two rows, the lower or inner row the larger. 
I have had the opportunity of examining Professor Dana’s original 
type of Leconte’s, contained in the museum of Yale College. It was, 
when received, broken and dried up, but with the carapace preserved, 
while the caudal appendages were wanting. The specimen was labeled 
‘Rocky Mountains, near Long’s Peak.” ‘This would place it within the 
present limits of Colorado. 
Four specimens from the museum of the Chicago Academy of Sciences, 
received through the late Dr. William Simpson, were labeled “Texas, J. 
H. Clark No. 3.” They only differ from Dana’s type specimen in the 
dorsal carina of the carapace being considerably shorter than in the 
type, being twice as long as the distance from the front margin of the 
carapace to the anterior end of the keel. 
In the other specimen this distance is one-third or one-fourth as great 
as the length of the keel. The specimens vary somewhat in the relative 
length of the keel, in the length of the abdomen, and the size and num- 
ber of spines on the under surface of the telson, while the endites of 
the Ist pair of feet vary slightly in length. The size and form of the 
telson, and the number and arrangement of the spines afford good spe- 
cific characters in this genus. 
Three specimens labeled “ Pools near Yellowstone River, Dr. Hayden, 
6,” were also received through Dr. Stimpson, of the Chicago Academy. 
The range of the species would seem to be from the Yellowstone River 
along the eastern flank of the Rocky Mountains to Texas, probably the 
upper part of the State. 
James, in Long’s “ Expedition to the Rocky Mountains,” says of this 
species: ‘“Rain-water puddles on the Platte River, near the Rocky 
Mountains. . . . In rain-water puddles we remarked a new species 
of Branchipoda belonging to the genus Apus; small crustaceous ani- 
mals, which exhibit a miniature resemblance to the King or Horse-shoe 
Crab (Limulus polyphemus) of our own sea coast, but which are furnished 
with about 60 pairs of feet, and swim upon their back. The basins of 
water which contained them had been very much diminished by evap- 
oration and infiltration, and were now crowded to excess, principally 
with the Apus, great numbers of which were dying upon the surround- 
ing mud, whence the water had receded. This species is distinguished 
from the productus of Bose and montagui of Leach, by not having the 
dorsal carina prolonged in a point behind; and from caneriformis by the 
greater proportional width of the thorax, and more obtuse emargina- 
tion behind. The length of the thorax along the middle is three-tenths 
of an inch, and its greatest breadth somewhat more. It may be named 
Apus obtusus.”—Note 7, p. 336. 
