TRANSLATIONS AND NOTICES 



GEOLOGICAL MEMOIRS. 



A. Th. v. Middendorff's Sibirische Reise. (Fossile Fische, 

 bearbeitet v. Johannes Muller), St. Petersburg, 1847. 



[Description of fossil fisli from Siberia, by J. Miiller.] 



The impressions of fish from Siberia, whicli are the object of the pre- 

 sent memoir, occur in a thick grey shale, which besides the carapace 

 of a crustacean, also contains remains of the larvae of insects and 

 a Helix. The shells represented of the natural size at pi. 11 *, 

 fig. 6. are the most abundant. They have no resemblance whatever 

 to the shells of bivalve mollusca, either with regard to their general 

 form, their extraordinary thinness, or their microscopical structure ; 

 they have however the most complete analogy with the shells of cer- 

 tain Crustacea, particularly the genus Limnadia. I have compared 

 slices of the fossil shells with those of Limnadia under the microscope, 

 and find them to agree in every respect. These fossil shells therefore 

 undoubtedly belong to a crustacean closely allied to this genus, if 

 not indeed identical with it. This is a circumstance of great im- 

 portance in deciding the nature of these shales, inasmuch as the 

 existing LimnadicB live in fresh water. I should not, however, have 

 considered the resemblance of these shells to those of Limnadia 

 sufficient to prove this to be a freshwater formation, had not Herr 

 V. Middendorff lately informed me of the facts long ago observed by 

 him, which had convinced him when in Siberia that this was a fresh- 

 water deposit. First, the occurrence of the hind-body of the hirva 

 of an insect decidedly belonging to the Neuroptera, but which can- 

 not be referred to any of the existing genera of that division, as the 

 three long feathers at the posterior extremity resemble Ephemera, 

 while the processes of the body-rings at the side of the abdomen re- 

 mind us of Libellida and Mschna. Secondly, the occurrence of a 

 mollusk having a very great resemblance to Paludina. Herr v. 

 Middendorff* informed me that he had seen in Siberia a specimen of 

 shale, in which, together with impressions of fish, a shell (chiefly 

 as casts) occurred closely resembling a Paludina, particularly a half- 

 grown P. vivipara. Amongst the specimens of shale with impres- 



* The plale does not accompany this Translation. 

 VOL. VI. — PART II. E 



