RUPERT JOKES OK THE EOSSIL ESTHERIiE. 265 
day; and, indeed, as far as tlie carapace-valves are concerned, this 
and the other so-called Posidonomyce referred to correspond to the 
PJstheria of Riippell and Baird * * * § ( Isaura , Joly; Cyzicus, Audouin). 
Different species of these fossil Pstlierice occur in the Devonian 
rocks (Caithness, Orkney, Livonia, and Russia) ; Carboniferous 
(Scotland, Berwickshire, Lancashire, Derbyshire, Belgium, France, 
Bavaria, and Silesia) ; Permian (Ireland, Saxony, and Russia) ; Tri- 
assic (England, France, and Germany); Rhsetie (Somerset, Glouces¬ 
tershire, Warwickshire, Worcestershire, and Elgin) ; Oolitic (Skye 
and Scarborough) ; and Wealden (Sussex and Hanover). Others 
are met with in the coal-fields of Lower Mesozoic age, in North 
and South Carolina and Virginia, and along their north-western 
extension, forming the so-called “ New Red Sandstone” of Penn¬ 
sylvania ;f and in the plant-bearing sandstones of India (Mangali, 
Panchet, and Kota) ; and in beds of undetermined age in Siberia 
(Tertiary?) and South America (Mesozoic?). 
Although occurring so constantly in the different geological 
periods, from the Devonian to the Wealden, J and again in some 
Tertiary beds and in the recent fresh waters, yet it is in the Rhsetie 
and Triassic deposits of Britain and the Continent, in the carbona¬ 
ceous shales of Pennsylvania, Virginia, and the Carolinas, and in the 
plant-bearing beds of India, that this little Bivalved Entomostracan 
appears to be pre-eminently abundant, so as to serve probably as a 
faithful index of a peculiar geological horizon. § 
In like manner, among the still lower forms of life, the Num- 
mulite is represented in the Carboniferous, Liassic, Oolitic, and 
Cretaceous rocks, and exists also at the present day ; but it particu¬ 
larly distinguished one epoch (the Tertiary) by a surprising fecundity 
and a temporary profusion of individuals. 
The occurrence of a fossil Pstheria in the Upper Sandstone and 
Shale of the Scarborough district ( E . concentrica , Bean,|| sp.) is of 
considerable interest, as indicative of the association of this crusta¬ 
cean genus with the Jurassic flora in England, as it is with a some¬ 
what similar flora in India and North America. 
In India a Labyrinthodont reptile (Brochiops laticeps) 9 ^ is found 
in the same strata as yield Pstheria at Mangali, possibly contempo¬ 
raneous, or nearly so, with those containing plants at Nagpur; near 
Panchet also, in north-eastern India, Pstheria occurs in equivalent 
* Proc. Zool. Soc. part 17, 1849, p. 87. 
t Continuous with the sandstones of New Jersey, and most probably with 
those of Connecticut also. 
f I have no satisfactory evidence of the presence of the genus in question in 
the Cretaceous deposits, excepting in their freshwater “ Wealden” equivalent. 
§ Prof. W. B. Rogers has already pointed out (Boston Nat. Hist. Soc. Proc. 
v. p. 15, &c.) the probable value of this little fossil in the comparison of the Meso¬ 
zoic rocks of North Carolina and Virginia, and of these with the so-called Triassic 
beds of the United States. 
|| Mag. Nat. Hist. vol. ix. p. 376. 
*[[ Quart. Journ. Geol. Soc. vol. ix. pp. 37 and 371. 
