Miscellaneous. 105 



Although occurring so constantly in the different geological pe- 

 riods, from the Devonian to the Wealden*, and again in the recent 

 marine and fresh waters, yet it is in the Triassic deposits of England 

 and the Continent, in the sandstones and shales of Virginia and 

 Pennsylvania, and in the plant-bearing beds of Virginia and Central 

 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 horizonf. 



In like manner, among the still lower forms of life, the Nummu- 

 lite is represented in the Silurian ;(:, Carboniferous, Liassic, and 

 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 laticeps^) 

 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 Penusylvanian 

 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 ff 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 



* I have no satisfactory evidence of the presence of the genus in question in 

 the Cretaceous and Tertiary deposits. 



t Prof. W. B. Rogers has already pointed out (foe. cit.) the probable value of 

 this little fossil in the comparison of the Mesozoic rocks of North Carolina and 

 Virginia, and of these with the so-called Triassic beds of the United States. 



% Annals and Mag. Nat. Hist. ser. 2. vol. xv. p. 58. 



§ Mag. Nat. Hist. ix. p. 376. 



II Quart. Joum. Geol. Soc. vol. ix. p. 37 & 371. 



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

 p. 185 ; and on Centemodon mlcatus, Proc. Ac. N. Sc. Philad. vol. viii. p. 17. 



** Leidy on Bathygnathm borealis, Journ. Acad. N. Sc. Philad. n. s. vol. ii. 

 p. 327. 



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



