476 J. M. Clarke—New Phyllopod Crustaceans. 
embodying the results of experiment. In no pea so far- 
as the writer is aware, do they conflict with the results of ex- 
periment, or require the aid of worn and ioroed. hyphens 
to bring them into harmony therew 
In this respect, the spaces tts theory of light stands in 
marked contrast with that theory in which the properties of an 
elastic ste are attributed to the ether,—a contrast which was- 
very distinct in Maxwell’s derivation of Fresnel’s laws from 
electrical puceliee, but becomes more striking as we follow 
the subject farther into its details, and take account of the 
want 8 absolute scraped in the medium, so as to embrace- 
nomena of the dispersion of colors and circular and 
eile ptiont aden 
Art. LV.— New Phyllopod Crustaceans Jrom the Devonian of 
Western New York; by JoHN M. CLarkeE, Smith College. 
With a Plate (annumbered.) 
Estheria pulex,n. sp. Plate, fig. 4. 
IN examining some fragments of soft, olive- colored shale- 
from near the base of the Hamilton proper, in Miles’ Gully, 
Hopewell, Ontario Co., I have detected the above representa- 
tive of this extremely pe coe The little pet ee 
are never more than in wi Fae in length, a 
described as having the ula margin nearly semi- Girkulay 
e beak central or very slightly solenior hinge line sloping 
tay, The surface is marked by six, or in the largest. 
seven, concentric ridges which are very broad with narrow in- 
tervenin g furrows. There appears to be no more elaborate: 
sculpturing of the carapaces than Jones has figured for his. ° 
. membranacea, which is the simplest of any as yet. 
noticed. 
It is irene to notice that this Estherca, the first ever 
found the Trias in America and nowhere at so low an 
horizon a et resembles in its sub- a beak, its outline- 
and surface markings, this species just referred to, E. mem- 
branacea Jones, from the Old Red of at as while all others . 
figured by that author (Mon. Esth. Paleontogr. Soc., vol. xviii) 
are from higher horizons, have the beak anterior, and the out- 
line of the carapace more nearly sub-trigonal. 
recent Hstherie vie found in fresh, or, in possible cases, 
brackish waters. In some general remark in thie connection. 
Jones has said that “seeing that Estherie appear in pools and 
ditches of rain-water, it is not unlikely that pools of fresh water- 
temporarily formed on a flat sea-shore may have been inhab bited: oe 
