1856.] JONES ESTHERIA MINUTA. 377 



Oolitic rocks, and exists also at the present day ; but it particularly 

 distinguished one epoch (the Tertiary) by a surprising fecundity 

 and a temporary profusion of individuals. 



The occurrence of a fossil Estheria in the Upper Sandstone and 

 Shale of the Scarborough district {E. concentrica. Bean*, sp.) is of 

 interest, as being indicative of the association of this Crustacean with 

 the Oolitic flora in England, as it is in India and America. 



In India a Triassic Labyrinthodont Reptile {Brachiops laticepsf) 

 is found in the same strata as yield the Estheria at Mangali and the 

 plants at Nagpur ; and in Pennsylvania reptilian remains % occur 

 with the so-called **Posidonia" : in America indeed the evidence 

 seems to point to a contemporaneity of the Virginian plant-beds, 

 the shales and sandstones of Pennsylvania and New Jersey, the foot- 

 marked sandstones of Connecticut, and the upper red sandstone of 

 Nova Scotia and Prince Edward's Island, which is also reptilife- 

 rous § ; and it is evident that in the Virginian and Pennsylvanian 

 shales the minute Crustaceans under notice are important fossils. 

 The plants of Nagpur and Virginia having a Jurassic facies, like 

 those of Scarborough, it will be interesting, as further evidences 

 turn up, to see how far we are to regard the Triassic or the Jurassic 

 element as preponderating, or whether a passage-group of deposits 

 are indicated by the evidence, — or, lastly, whether these Plant-beds 

 with Reptiles and Crustaceans indicate the terrestrial and lacustrine 

 conditions only of the early secondary period. 



The Jurassic flora of Australia 1| and that of Southern Africa have 

 been hitherto collected without affording any clear traces of the 

 Estheria. The latter country, however, has its probably Triassic 

 Reptile, the BicynodoUy imbedded with this flora 1[ ; — so that the 

 peculiar association above-indicated for India and North America 

 obtains there also. 



In pointing out these facts of the geological and geographical dis- 

 tribution of the fossil Estheria^ I merely touch upon the salient 

 points of an interesting subject of research, — for the elucidation of 

 which careful inquiry at home and abroad is still requisite. 



In conclusion, although the recent Estheria is a marine Crustacean, 

 yet, since very closely allied forms are of freshwater habits, and since 

 among bivalved Entomostracans different species of a genus and even 

 the individuals of a species occasionally live either in marine or 

 in fresh water, there is no certain evidence afforded by the fossil in 

 question whether the so-called Triassic deposits in which it is found 

 were formed in rivers, lakes, or seas. 



* Mag. Nat. Hist. ix. p. 376. 



t Quart. Journ. GeoL Soc. vol. ix. p. 37 & 371. 



% Lea on Clepsysaurus Pennsylvanicus, Journ. Acad. N. Sc. Philad. n. s. vol. ii. 

 p. 185 ; and on Centemodon sulcatus, Proc. Ac. N. Sc. Philad. vol. viii. p. 77. 



§ Leidy on Bathygnathus borealis, Journ. Acad. N. Sc. Philad. n. s. vol, ii. 

 p. 327. 



Ij See M'Coy's paper, Annals and Mag. Nat. Hist. vol. xx. p. 145, &c. 



% Trans. GeoL Soc. 2nd series, vol. vii. part 4. p. 227, note. 



