PACKARD.] PHYLLOPODS OF NORTH AMERICA. ' 355 
three hundred miles west of the Missouri River, the Smoky Hill River 
is twelve miles south. The ‘divide’ between it and Big Creek, one of 
its tributaries (upon which Ellisis situated), is about one-third of the 
distance, or four miles. Six miles north is a tributary of the Saline 
River, with a “divide” about midway between it and Big Creek. From 
these “«iivides,” at varied intervals, are ravines, those upon the north 
side often deep enough to be called cafions, and in some of which are 
small springs, sufficient to maintain pools containing fishes (and Amphi- 
pods). ‘The ravines from the south of these ‘divides’ are more gentle 
or less abrupt, and though, upon heavy rains, torrents of 8, 10, or more 
feet of depth, rush down them, they are ordinarily dry pools of water 
remaining only two or three weeks at the angles where are bluff banks, 
or in other excavated places. In such pools, well up the ravines be- 
yond where fishes from the creek run up during the flood, these Crusta- 
ceans are found. They are not found in ‘butfalo wallows,’ or in any 
upland pools. Under the circumstances of this year or last only three 
or four weeks of life can they have. Millions of them perish by the 
drying up of the pools in July. A less number hatch out after the fall 
rains, and they can have hardly more than a month to live.’ 
Il.—THE GEOLOGICAL SUCCESSION OF THE PHYLLOPODA, 
FOSSIL FORMS. 
Up to this date but four species of fossil Phyllopoda are known from 
North America; these are: 
Estheria pulex Clarke;* from the base of the Hamilton shale in New 
York. 
Eistheria ovata T. R. Jones; from the Triassic beds of North Carolina, 
Virginia, and Pennsylvania. 
Estheria dawsoni Packard; from the Quaternary Clays of Canada. 
. Leaia leidyi, T. R. Jones; from the Lower Carboniferous of Pennsyl- 
vania. 
We reproduce the descriptions of the forms described by Prof. T. R. 
Jones from his monograph of the fossil Estheriz. London Palontologi- ' 
cal Society, 1862. . 
* Estheria pulex Clarke, Amer. Journ. Se. June, 1882, 476. 
“Tn examining some fragments of soft, olive-colored shale from near the base of the 
Hamilton proper, in Miles’ Gully, Hopewell, Ontario County [N. Y.], I have detected 
the above representative of this extremely interesting genus. The httle carapaces are 
never more than #™™ in width and 4™™ in length, and may be described as having 
the ventral margin nearly semi-circular, the beak central or very slightly anterior, 
hinge line sloping laterally. The surface is marked by six, or in the largest seven, 
concentric ridges, which are very broad, with narrow intervening furrows. ‘There ap- 
pears to be no more elaborate sculpturing of the carapaces than Jones has figured for 
his species, LZ. membranacea, which is the simplest of any as yet noticed. 
“‘Tt is interesting to notice that this Hstheria, the first ever found below the Trias 
in America, and nowhere at so low a horizon as this, resembles in its subcentral heak, 
its outline and surface markings, this species just referred to, LZ. membranacea Jones, 
from the Old Red of Caithness, while all others figured by that author (Mon. Esth. 
Paleontogr. Society, vol. xviii) all from higher horizons, have the beak anterior and 
the outline of the carapace more nearly subtrigonal.” 
This is a very remarkable species of Hstheria, and may yet be found to represent an 
undescribed genus. It differs from any species of the genus figured by Jones, inelud- 
ing L..membranacea, in wanting a straight hinge-margin. Its small size, few lines of 
growth, and lack of a hinge-margin, indicate that it is very young, and for that reason 
may yet prove to be a true Estheria. 
