100 . POSSIL ESTHERIiE. 



10. EsTHEiuA MuiicHisoNi^, spec. IIOV. P]. Ill, figs. 1 — 12. 



Telijna (?), Murchison. Transact. Geol. Soc, 2nd ser., 1827, vol. ii, p. 311. 



Inch. Inch. 



Height 

 Length 



3^ ^Proportion 27 to 42, or 1 : l| + 

 Ti- 



Height, more than ^^"^ 



Length ,|jProportion 17 to 33, or 1 : 2- 



Carapace-valve nearly elliptical, the straight hinge-line interfering Avith the symmetry 

 of the outline. The umbo is forward, at the end of the hinge-line, and scarcely affects 

 the outline. The anterior extremity has a flatter curve than the posterior. About 

 eighteen delicate concentric ridges are usually distinctly to be observed, with their rather 

 wide interspaces (figs. 1, 3, 4, 5, &c.) ; but some carapaces have nearly thirty ridges, with 

 very narrow interspaces (figs. 2, 6, 7). The ornament of the interspaces is essentially a 

 bold, irregularly hexagonal reticulation (figs. 5 and 12), like that of ^. minuta (PI. II, 

 fig. 3) ; but it generally takes on (or passes into) a distinct, short, vertical wrinkling at 

 the lower part of the interspace (figs. 5, 7, 11). This sometimes presents the modification 

 seen in figs. 3 and 8, where the wrinkling is of a much smaller pattern, and reaches half 

 way up, or all across, the interspace. Sometimes a delicate, horizontal wrinkling inter- 

 feres with (fig. 4), or replaces (fig. 9) the vertical wrinkles, without hiding altogether the 

 reticulate structure of the shell. Not unfrequently, both the broad and the narrow inter- 

 spaces are blank (figs. 6 and 10). 



The carapace-valves of this beautiful Estheria have been converted into calcite, but are 

 otherwise little altered by fossilization, except being somewhat compressed and rendered 

 silvery white, and will bear comparison with the carapaces of any recent JEsiheria. Nor 

 have we far to seek for a modern representative of this Jurassic form. E. Daha- 

 lacensis, Durckh. (from the freshwater marshes of the Island Dahalac, Abyssinia), figured 

 and described by Dr. Baird, ' Zool. Soc. Proceed.,' 1849, p. 89; Anmdosa, pi. 17, 

 figs. 2 — 4, has but a trifling difference in the outline and the number of ridges ; and 

 its reticulate ornament is the same as that of E. MurcJiisonia, except that the tendency 

 to dev elope the vertical wrinkles seems to be wanting. But the latter ornament, asso- 

 ciated with the reticulation, just as in E. MurcJiisonia, is beautifully shown in a somewhat 

 differently shaped Estheria from India {E. Boysii, Baird, ' Proc. Zool. Soc.,' 1839, p. 89, 

 Ammlosa, pi. 11, fig. 6). 



In the Museum of the Geological Society, among a collection of fossils brought from 

 the Western Islands of Scotland by Sir Roderick Murchison in 1827, is a specimen of 

 bluish marl from Skye, labelled " Canal, Icolmkill, Skye," bearing on one surface a crowded 

 layer of the delicate Estheria described above. These are alluded to by Sir R. Murchison 

 as " Tellince (?) " in his memoir " On the Coal-field of Brora, in Sutherlandshire, and some 

 other Stratified Deposits in the North of Scotland," in the ' Transact. Geol. Soc.,' 2nd 



