74 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Dec. 3. 



is an inch long, and Esiheria striata of the Coal, which is as large). 

 The valves are frequently (if not mostly) in pairs, closely adpressed, 

 as if the animals had been suddenly imbedded ; and this is apparently 

 the case on the several planes of bedding which their abundant 

 presence makes so readily apparent in the fissile shale. Rarely, 

 however, are the valves perfect ; their tenuity and a slight lateral 

 shift, which oblique pressure has given them, have led to their being 

 crushed and wrinkled, and the two separated faces of a bed-plane 

 divide unequally between them concentric portions of the light-brown, 

 glossy, thin, corneous valves. The umbones are usually wanting. 



Putting aside the wrinkles (mechanically formed) that affect the 

 carapaces, we see, with a low power of the microscope, a delicate, 

 raised reticulation between the concentric ridges, the meshes often 

 passing into irregular, anastomosing riblets, perpendicular to the 

 ridges. The usual ornamentation of Estheria is some reticulate 

 sculpturing of the interspaces between the ridges ; and this is not 

 unfrequently modified by passing into vertical riblets : still, different 

 patterns or modifications are recognizable in the several species of 

 Estheria ; and the bold freedom of the delicate re ticulo -linear orna- 

 ment in this case differs from all the other patterns that I know of. 

 The carapace of E. Middendorfii approaches in general appearance 

 that of E. Dalialacensis (Durckheim), from the freshwater marshes 

 of Dahalac, off the coast of Abyssinia, and found also in stagnant 

 water on the banks of the Tigris by the late W. Kennett Loftus ; 

 and the reticulation of the two sj^ecies would be similar, did it not lose 

 itself in riblets in the former. Though the carapaces seem to have 

 been, at least in many instances, imbedded whole, yet they do not 

 appear to contain any limbs or remains of the body, with the ex- 

 ception, in one or two individuals, of what may be ova ; these are 

 numerous little globular bodies, occasionally somewhat crushed, and 

 about -^th of an inch in diameter. 



The slightly indurated condition of the shale gives it a modern 

 appearance ; but there is a want of collateral evidence as to its 

 geological age, excepting in the case of the little Fish that occurs in 

 considerable abundance in the deposit, both with and without the 

 Estheria. This Fish is termed Lycojotera Middendorfii by J. Miiller ; 

 but Sir P. Egerton informs me that he has no doubt of its being 

 either an Aspius or some closely allied genus. Aspius (a Cyprinoid) 

 is found in some Miocene freshwater strata in Europe. 



Limnams seems also to have been found with the Estheria, both 

 by von Middendorf and Mr. C. Austin, as well as a few fragments 

 of Insects and some remains of Plants ; and hence there is here, as 

 in most other fossil occurrences of Estheria, every reason to believe 

 the deposit to be of freshwater formation. 



