RUPERT JONES ON THE EOSSIL ESTHERIJE. 
275 
A general crumpling of the shell of a very thin Avicula or Posi- 
donomya irregularly corrugates the whole surface, concentric wrinkles 
and all; but in Estheria the true ridges are seldom thus interfered 
with, but rather yield to the transverse pressure by taking on an 
obliquity of direction, leaving the sculptured interspaces to show the 
crumpling effect of pressure. Barely converted into calcareous mat¬ 
ter, the Estherian carapaces usually present a delicate, brownish, 
horn-like tissue, generally with some degree of transparency and 
polish, contrasting with the dull and perfectly calcified shells of the 
Aviculidce , or their bold wide-ridged impressions, black and filmy, or 
delicately nacreous. In carbonaceous deposits the Esther ice often 
leave only black films or merely impressions. In one case a white 
siliceous (?) substance is found to replace the valves in a lignite 
(Lettenkohle). Sometimes a ferruginous film has replaced the cara¬ 
pace-valves, especially in sandstone. 
As Estheria minuta has been referred to Posidonomya so generally 
and for so long a time, it is highly probable that other little fossils 
of the same class still pass as Aviculidce in palseontographical works 
and in collections. # That attention might be turned to these, I would 
point out some figured specimens which appear worthy of special 
microscopical examination. The small shells figured by Pusch (‘ Polen’s 
Pakeontolog.,’ pi. 5, fig. 14) as the young of Ctatillus Brongniarti have 
a strong resemblance to Estheria , and are the more worthy of exami¬ 
nation as they are said to come from the clay-beds above the Juras¬ 
sic limestone. Pigs. 11 and 12 of pi. 37 of Beuss’s ‘ Kreideform. 
Bohm.’ are not so promising; they may really belong to Inoceramus 
Crispii and I. planus, to which they are referred. Some of the fossils 
figured in pi. 17 of Lynch’s ■ Beport on the Geology of the Dead 
Sea’ might possibly be worth re-examination ; also the Australian 
fossil figured in ‘ Annals Nat. Hist.’ vol. xx. pi. 13, fig. 3. The Posi- 
donomya Wengensis , Wissman, and Avicula globulus , Wissm. ‘ Muns¬ 
ter’s Beitrage,’ iv. p. 23, pi. 16, figs. 12 and 13, from the St. Cassian 
beds of the Tyrol, should certainly be looked at by a carcinologist. 
Cardinia nana, de Koninck, ‘Anim. foss. Terr. Carb. Belg.’ p. 71, 
pi. 1, fig. 6, is another little shell to be examined. In the ‘ Geognos- 
tische Skizze der Umgegend von Ilmenau am Thiiringen-Walde ’ 
(Zeitschr. deutsch. geol. Gesell. xii. 1860), Herr Karl von Eritsch 
remarks (p. 144), “ Near Goldlauter, not far from Ilmenau, some 
beds are nearly full of C. nana. These flattened shells remind one of 
the Triassic Posidonomya minuta , Bronn. Perhaps it is the same 
shell as von Gutbier mentions in his ‘ Yersteinerung. des Bothlie- 
gendes in Sachsen,’ p. 7.” 
The long-continued existence of the genus Estheria , from a very 
early period (Devonian) to the present, is a fact of considerable 
* Prof. M’Coy has already intimated that some so-called fossil shells may be 
Entomostraca; (‘Synopsis of Carboniferous Fossils of Ireland,’ 1842, p. 164.) 
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