78 FOSSIL ESTHERLE. 



as in the Keuper, we may suppose that the Estheria flourished in brackish, if not in fresh, 

 water, at intervals when the saltness of the sea was more or less reduced by the land- 

 waters. 



The absence of Estheria in the Rhgetic beds (or Avicula contorta zone) of Germany 

 is coincident, apparently, with their more decidedly marine character ; and so also the 

 apparent absence of Estheria in the Triassic beds of the Alps, with their many fos- 

 siliferous strata, may be due to more constant marine conditions having obtained during 

 the Triassic period in that area than in the Western European region. 



7. Estheria Mangaliensis, spec. nov. PL II, figs. 16 — 23. 



Estheria, Hislop. Quart. Journ. Geol. Soc, vol. x, p. 4/2 ; vol. xi, p. 3/1 ; vol. xvii, pp. 347, 353. 

 — Jones. Ibid., vol. xii, p. 377. 



Inch. . Inch. Inch. 



Height T ^ ll less than T \ 



Length, less than 4t 



a " 12 



Proportion 1^:2 1:1+ 1 : 1J— 



Carapace-valves usually broadly subovate (fig. 16), but varying from subtriangular 

 (fig. 20) to suboblong (fig. 21), according to age, sex (?), and state of preservation. 



In fig. 20 the anterior extremity is truncate, advancing but little beyond the umbo ; 

 but usually it curves out boldly from beneath the umbo, not unfrequently with as full a 

 curvature as that of the posterior margin (figs. 21, 23) ; normally, however, the valve 

 appears to be somewhat narrower in front than behind (figs. 16, 22). The hinge-line, 

 terminated in front by the umbo, is well marked ; in the majority of specimens it is 

 equal to rather more than half the length of the valve (figs. 16, 21) ; but in others it is 

 little more than a third (figs. 20, 23). 



Ridges about fifteen ; but in adults they are crowded in increasing numbers towards 

 the ventral border, and become merely the overlapping flat edges of the periodical layers of 

 the carapace ; this is well seen where the growth has been irregular, owing to some local 

 accident (fig. 19). The interspaces are broad and smooth, presenting here and there an 

 obscurely hexagonal reticulation of small meshes (figs. 17, 18). 



A remarkable similarity exists between this fossil form found at Mangali and a recent 

 Estheria, living in the pools near Jerusalem, figured and described by Dr. Baird as 

 E. Gihoni (' Annal. Nat. Hist.,' ser. 3, vol. iv, p. 281, pi. v, fig. 1). The valves of the 

 latter, however, have fewer ridges and wider interspaces ; and its ornament is a far bolder 

 reticulation than that exhibited by the fossil ; were E. Gihoni fossilized, however, it 

 would be with difficulty distinguished from E. Mangaliensis} 



At Mangali, in Central India, about sixty miles south of Nagpur, the Rev. Messrs. 



1 In the 'Memoirs of the Geological Survey of India,' vol. iii, p. 197, Dr. Oldham has by mistake 

 stated that Mr. Hislop's specimens of Estheria from Mangali were identified by me with E. minuta. 



