112 FOSSIL ESTHERIiE. 



thickly strewed with flattened carapaces of Estheria, accompanied with an occasional small 

 Fish, 1 represented by a dark stain and the skeleton. In other specimens the Fishes 

 are abundant, and the Crustaceans rare. Both valves of the carapace are in most 

 cases present, and but little displaced ; and sometimes what appear to have been the ova 

 of the Estheria have left traces, in the form of small, globular grains. No other remnants 

 of the organs of the animal have been discerned, although the thinness of the carapace, as 

 delicate as the wing of an insect, would allow of such being seen. The valves have a 

 light-brown colour, and are for the most part glossy along fine lines, corresponding 

 chiefly to the concentric ridges, which present more solid, chitonous carapace-matter, 

 whilst the finely reticulate interspaces do not reflect the light so readily. Frequently the 

 valves are more or less crumpled with small, transverse wrinkles. 



We have no finished sketch of E. Middendorfii on PI. IV, on which the size of the 

 valve is shown by fig. 12 ; the outline, magnified six times, for comparison with all the other 

 Estherian valves figured on the same scale, is shown by fig. 13. The reticulated surface 

 is shown on the lower part of fig. 1 6 ; the interior cast (on the shale) of that network is 

 seen in the upper part of the same ; the ova also are seen here, and more highly magnified 

 in figs. 20, 21, 22. Fig. 17 is the natural cast of a reticulated interspace, somewhat 

 resembling that in the lower part of fig. 16 ; fig. 14 is a similar cast of an interspace, 

 having transverse riblets ; and fig. 15 represents the ribbed interspace, restored by Mr. 

 G. West, with setaceous ridges, that have left evidence of either setae or rugag in 

 the specimen shown in fig. 14. Another natural cast of a reticulated interspace is given 

 in fig. 18, but the clay has here replaced the raised network. 



The first notice of E. Middendorfii is in Dr. A. Th. von Middendorf s ' Sibirische Reise/ 

 Band i, Theil 1 (" Einleitung ; Klimatologie ; Geognosie"), ' Fossile F'ische,' Bearbeitet von 

 Joannes Mliller, 2 p. 259, &c. Dr. Midler here describes the little fossil Fish, Lycojdera 

 Middendorfii (which Sir P. Egerton informs me is probably an Aspius), together with a 

 .bivalved Crustacean, Limn a di a (my E. Middendorfii). A larva of an Insect, probably 

 ncuropterous (neither Ephemera nor uEsc/tna, but supposed to be possibly allied to both), 

 and an obscure Paludina-like shell, were the only other fossils found in the Estherian 

 shale. The Fish (figs. 1 — 5), the Crustacean (fig. C), and the Larva (fig. 7), are 

 carefully figured in pi. 11 of the work alluded to. At pp. 263 and 264 the shale and 

 its locality are thus described by Von Middendorf: 



"About 140 to 150 versts south of Nertschinsk, and some 70 versts from the nearest 

 point of the Chinese frontier, a river named By'rka falls into the right side of the Turga, 

 at 40 versts above the confluence of the Turga with the Onon, into which the Turga also 

 empties itself from the right. From the above-mentioned mouth of the B)'rka downwards, 

 a shaly clay forms the right bank of the Turga, which has cut for itself a deep and pre- 



1 Aspius or some closely allied genus ; according to Sir P. Egerton, Bnrt., F.R.S., &c. 

 See also the 'Quart. Journ. Geol. Soc.,' vol. vi, part 2, "Miscell.," p. 45. 



