360 GEOLOGICAL SURVEY OF THE TERRITORIES. 
FUSS os deosssesoke Estheria ovata (Lea) ............-----s---- '.---| United States, Pennsylvania, 
Virginia, North Carolina. 
Estheria mangaliensis Jones ...--------------- India. 
Rhee ticue ssi eeaee cece | Estheria minuta (Alberti) var. brodieana -..--. England. 
Rheetic or Jurassic... .- | Estheria kotahensis Jones ..-...5...-------.--- India. ee 
ING MOR Ssoeeoeoseoenone Estheria minuta (Alberti) .......-...----..... Hanover, Germany, England, 
IkCoUH IEW CSoo dod Losaoos 
Lettenkohle ....-.--.. Estheria minutia and ‘‘Apus” ...---.....2------ France, Germany. 
Buber sees ee eee ne 
Permiamye ee eeeeeesose Estheria exigua Hichwald......-----.--.------ Russia. 
Listheria portlockia Jones.-... ..-..-..--------- Treland. 
Estheria tenella Jordan ..--....-..------------ Saxony. 
Upper Carboniferous ..| Leaia leidyi (Lea) var. williamsoniana Jones..| England. 
Estheria tenella (Jordan).........---------.--. France, England, Germany. 
Middle Carboniferous..| Hstheria beinertiana Jones.-........-------.--- Engl land. 
Estheria striata (Miinster) ..-.-..-.-.-.--.-.-. Bavaria, Belgium. 
Lower Carboniferous ..| Hstheria striata (Minster) var. tateana.-.---- England. 
Estheria striata var. beinertiana.......------- Silesia, England, Scotland. 
Estheria striata var. binneyana .......-.------ England. 
DU BTIG RUCHED ERG io SAS SA AASB BOGE Ses O OR SOE Pennsylvania. 
Leaia leidyi var. SalLeriN Tame aan ee nae Scotland. 
Devomiany cesses sceeeee Estheria membranacea Pacht ..........--.-.-. Livonia and Scotland. 
It appears from the foregoing table that the oldest Phyllopod crusta- 
- Gean is a genuine Estheria,* judging, of course, from the carapace valves 
alone ; the more or less problematical form, Leaia, being carboniferous. 
Thus Estheria dates from the Devonian. 
As to the ancestral forms of Phyllopods in general, they may have 
been derived from forms like the Cladocera. Limmetis indicates in its 
resemblance to Daphnia, that from this Branchiopod with its cladoverous 
allies the Phyllopods may have sprung. Next below the Branchiopods 
stand the Copepoda from which all the other Neocarida have sprung; 
the Copepoda all originating from a nauplius ancestor. The Ostracoda, 
the lowest suborder of Branchiopoda, flourished in the Lower Silurian 
seas, hence the Branchiopoda must have originated in the Laurentian 
period and the Phyllopod suborder at least as early as the Upper Silu- 
rian period. 
The accompanying table may serve to give a rude idea of the rela- 
tions of the principal groups of the Orustacea, and their appearance in 
geological history, so far as the extremely scanty data we possess will 
allow, while the diagram may also serve as a genealogical tree, shuwing 
the probable origin ‘of the main divisions of the Crustacea. 
As is well known, the Trilobites are met with in comparative abund- 
ance in the lowest fossil iferous beds of the Silurian period, and they are 
the most ancient of Crustaceans, so far as their remains give evi- 
dence. The genera Conocephalites, Dicellocephalus, Paradoxides, and 
Agnostus, besides other forms, appear in the Potsdam sandstone or 
equivalent primordial rocks of this and other countries. The type dis- 
appeared during the Carboniferous period, the genera Phillipsia (one 
*As there exists some doubts in my mind as to the Estherian nature of EL. palex 
Clark, I have left this out of present consideration. 
