318 GEOLOGICAL SURVEY OF THE TERRITORIES. 
on the west bank of Frenchman’s River, Montana. You will noi find 
this stream on the map, perhaps, by this name. 
‘¢ Tt is one of the first of the whole series of similar streams flowing south 
into Milk River. The species was not observed elsewhere. The ponds 
were extensive shallow sheets of sweet water, of a comfortable wading- 
depth, generally with a little open space in the deepest part, but mostly 
choked with luxuriant vegetation (Graminece, Utricularia, &e. ). Date 
of collection, first week in J uly, 1874.” Thirty-two males and thirty-one 
females were obtained by Dr. Coues: this equality in the number of the 
sexes is noteworthy. 
Several females with eggs were also obtained by C. Carrington! of Hay- 
den’s U. 8. Geological Survey, at Smithfield, Cache Valley, Utah. The 
specimens are in the Museum of the Academy of Natural Sciences, 
Philadelphia, to the curator of which I am indebted for the opportunity 
of examining the specimens. 
LEPIDURUS BILOBATUS Packard. 
Plates XV, fig. 3; XVII, figs. 4,6; XXI, fig. 3. 
Lepidurus bilobatus Pack., Bull. U. 8. Geol. & Geogr. Survey, F. V. Hayden, in charge, 
iii, No. 1, 178, Fig. 17, April 9, 1877. 
10 ¢,3 2 .—Male.—Carapace broad and short; as broad as long, meas- 
ured along the median line. The eyes as in ZL. couesiti. The excavation 
in the front edge of the carapace is much larger and broader than in LZ. 
ceuesit, and the teeth are more numerous, but very unequal in size, there 
being a few large teeth, with a number of smaller ones between them. 
The abdomen is longer than usual, with six (and part of another) seg- 
ments beyond the last pair of feet, while in L. cowesti there are only five. 
The spines on the edges of the abdominal segments are larger than in 
D. coue ii, ircluding the five teeth on the edge of the segments as well 
as the spines. There are about sixteen segments beyond the posterior 
edge of the carapace; in DL. couesii, eight. On the dorsal side of the ab- 
dominal segments there are eight spines on the hinder edge, while there 
are nine in L. couesti. The species differs from any others in the re- 
markably short telson, which is short and broad, nearly one-half as long 
in proportion as in L. ‘couesii. The segment is broader at base and the 
telson is broader than in any other species; it is truncate at the end, 
and divided by a slight incision into two well-marked lobes, with about 
seven more or less well-marked median Spines on the blade of the tel- 
son; this segment, including the telson, is as long as the preceding seg- 
ments collectively. In the carapace, seen from “beneath, the distance 
from the anterior edge of the hypostoma to the anterior edge of the 
carapace is much less than in L. cowesit, while the hypostoma itself is 
much more convex. The Ist pair of legs are much longer and broader 
than in Z. cowesii, and the succeeding pair are rather broader than in 
that species. 
Length of body, including caudal stylets, 48™™; length of carapace 
(measured along median bb axe))5 Ieee breadth, gem, caudal appendages, 
17§™™; Ist pair of feet, 15™™. 
Female. —Ditfers from the male in the much shorter body and shorter 
first pair of feet. There are five segments beyond the last pair of feet, 
and twelve segments beyond the eds ge of the carapace. It is easily dis. 
tinguishable by the shorter abdomen and Ist pair of feet, but other- 
wise it does not differ, the telson and caudal filaments being ‘of the same 
proportion. The egg- sacs were empty; they are situated on the tenth 
