ESTHERIA TENELLA. 



31 



3. Estheria tenella, Jordan, sp. Plate I, figs. 26, 27; PI. II, fig. 39; and PL 5, 



figs. 1—7. 



Posjdonia (?), Michelin. Bullet. Soc. Geol. France, 1836, vol. vii, p. 321. 

 Cypris, A. D'Orbipny, 1845 ; Landriot. Ibid., 2d series, 1849, vol. vi, p. 90. 



— Naumann. Ibid., 2d series, 1848, vol. v, p. 301. 

 Posidonomya tenella, Jordan and H. G. Bronn. Neues Jahrb. f. Min., 1850, p. 577. 

 [? Estheria exigua, Eichwald, sp. See p. 37]. 



From the Mnrgthal and from ("Height of valve, less than A inch") _, 



.. x ix i , !> Proportion 5 to 7, 



Astlev (Lancashire) (.Length, rather more than -f a 



From Bradford (Lancashire). 

 From Oschatz 



i 



12 



f Height, more than 



\_Length, less than \i 



("Height 



LLength, less than 



H 



T2 



,. J 



;;} 



or 



From Lanarkshire fHeight, less than JL „ | 



(.Length, less than ■£% ,, J 



From Bradford (Lancashire).. 



J Height 



» 1 



,. J 



^Length, more than -fa 



_ .„ , _ , . . fHeight, more than A- ,, 1 



From Bradford (Lancashire) \ T 5 , " " > 



iLength ft „ J 



13 to 17, or 



8 to 11, or 

 17 to 23, or 



9 to 13, or 

 21 to 30, or 



1 : U- 

 1:H- 

 1 : H— 

 1: 1£+ 

 1 : H— 



l:lf 



Carapace-valves broadly subovate, oblong, or nearly quadrate ; hinge-line straight, but 

 rounding off before and behind insensibly into the well rounded extremities, which are 

 nearly symmetrically, but unequally, curved. The umbo is forward, at the front end of 

 the hinge-line, and does not interfere with the outline of the valve. Concentric ridges 

 about 15 ; interspaces minutely pitted by the meshes of a delicate reticulation. 



This Estheria occurs at several localities, and is essentially a member of the " Car- 

 boniferous " fauna, though it is found also in beds referred by some to the Permian 

 formation (Oschatz, Autun, and ? Russia). 



]. In the 'Neues Jahrbuch f. Min.,' &c, 1850, p. 577, Prof. H. G. Bronn gives an 

 account of the black shales of Sulzbach, Lebach, &c, and describes Posidonomya 

 tenella (Jordan) which there occurs in company with the interesting crustacean Gampsonyx 

 fimbriatw 1 (Jordan). "Posidonomya" is stated to lie very thickly on the faces of the 

 shale; to be of an oblique-oval shape, 3 — 4 millimetres in length, 2 with 8-10-15 concentric 

 wrinkles, which are the less numerous when they are large and strong ; the hinge-border join- 

 ing the hinder border with blunt but distinct angle. It is stated to be like P. Becheri 

 in miniature, and to correspond in form and wrinkles to fig. 6 a, pi. 113, of Goldfuss's 

 ' Petref.,' but of only half the size, and somewhat longer in proportion : the angles of the 



1 Palseontographica, vol. iv, p. 2. 



2 M. Jordan refers to some specimens 5 millem. {2\ lines, or |th inch) long ; N. Jahrb. 1850, p. 578. 



