ESTHERIA MINUTA. 57 





occur, they are never found in them. Such pseudomorphic salt-crystals occur near 

 Limeberg, in the shales with IAngula tenuissima, alternating with the limestones, just 

 above the Lettenkohle group ; in the dolomitic beds of which latter Estheria minuta 

 occurs (sparingly) with Myqphoria, &c. (See page 51.) So again, in England, the 

 pseudomorphic salt-crystals occur in the Upper Keuper shales immediately overlying the 

 grey sandstones and shales containing Estheria, but not in the Estherian shales themselves. 



Estheria minuta of the English Trias. 



In the New Red Sandstone of England Estheria minuta is abundant at places, and 

 often occurs as well-grown individuals (larger than any from the Continent that I have yet 

 had an opportunity of seeing), and occasionally (as at Pendock) most perfectly preserved. 

 Judging from the materials at my command, I may say, that the English specimens are 

 more variable in their shape than those found in Germany, since they are apt to contract 

 the posterior portion of the carapace-valves, and so take a subovate form ; but I cannot 

 say that such a variation of outline may not be found in the foreign specimens, of which 

 I have not seen a very large series. 



The beautifully perfect condition of the carapace in PI. II, fig. 1, is strongly con- 

 trasted, in its neatly definite concentric ridges, and the smooth broad intervals, delicately 

 reticulated by large fine-walled meshes, with the obscurely wrinkled stony casts, indicated 

 by figs. 4 and 5, and with the coarse-walled meshes into which the original reticulation 

 is here modified, the animals having been fossilized in a less accommodating matrix. The 

 German specimens (PI. I, figs. 28 — 30) have suffered similar deteriorations. 



The measurements of some of the best English specimens arc as follow : 



From Pendock 



Height, rather more than \\ inch] 



Length of valve -f| „ [Proportion, 2 to 3 by 1, or 



Thickness of closed valves, | ltoljby-y. 



less than ■£% „ 



Height \ -?— 



From Shrewley Common and J L ° tl \ J_ \ Proportion G to 9 by 4, or 1 to 



Pendock 



D * 12 " f Hby ». 



( Thickness rather less than ^ » J 4 



rHeight, rather less than T % inch") 

 From Somerton \L.n°-th A /Proportion 23 to 30, or 1 : 1^-f- 



In my examination of English specimens of Estheria minuta, I have had before me 

 specimens from the Upper Trias, or Keuper, of Somersetshire, Worcestershire, Warwick- 

 shire, and Leicestershire. 



1. A specimen of pinkish-white, fine-grained sandstone, from Shrewley Common, 

 Warwickshire, with convex casts of Estheria, retaining traces of the shell and its orna- 

 ment (PI. II, figs. 5 — 7), collected by the late Mr. H. E. Strickland, and presented by 



8 



