140 Reports and Proceedings — Geol. Soc. London. 



Stem-joints of a Crinoid resembling those of Bourgiieticriniis have 

 long been known in the Planerkalk of Streben (Elbe) ; but on the 

 diseoverj of the calyx it was found to differ considerably from that 

 genus. It was then referred to the genus Antedon by Prof. Geinitz. 

 Stems also resembling Bourgneticrinus have been found in the Upper 

 Chalk of Kopinge (S. Sweden), and a calyx resembling that de- 

 scribed by Prof. Geinitz has also been found. Prof. Lundgren 

 kindly entrusted this to the author for description. 



For these two fossils he considers not only a new genus but also a 

 new family required. He proposes for the former the name Mesa- 

 crinus, as the characters of its calyx ally it to the Pentacrinidse. 

 The author describes the characteristics of the genus Mesocrinus 

 and of the species M. suecica (the Swedish) species, and its 

 differences from M. Fischeri (from Streben), and discusses the 

 relationships of the genus, which combines the characters of a 

 Pent(fcriniis -csdyx with a Baurgueticrinus-stem. 



A new species of Comatula {Antedon impressa) from the Ignaberga 

 Limestone of Scania was also described, and its systematic position 

 discussed. 



Dr. Otto Hahn, of Eeutlingen, exhibited a large series of Micro- 

 scopic sections of Meteorites, in explanation of which the following 

 remarks were addressed to the President and Fellows present : — 



" Dr. Hahn, in inviting you to examine the mici'oscopical speci- 

 mens of meteorites which he has prepared, and in order to assist you 

 in determining the character of the forms and structures which you 

 will find exhibited in them, desii-es to present a short summary of 

 the negative considerations which forbid that such structures should 

 be classed among crystalline forrms. 



'' As is well known, the chondrites, the species of meteorites from 

 Vi^hich his specimens are prepared, consist, besides the metals which 

 they enclose, of the minerals enstatite and olivine. 



" In his work on the meteorites and their organisms, lately pub- 

 lished, Dr. Hahn has given photographs of 130 different forms and 

 structures. Now if these structures are crystalline, the two minerals 

 in question would present themselves in at least 130 different forms 

 and structures, although the absence of all structure is recognized as 

 a fundamental principle of the theory of minerals. 



" Again, the structures exhibited by the chondrites cannot be due 

 to slaty cleavage, since olivine has no slaty cleavage, and that of 

 enstatite and of other minerals does not appear under the micro- 

 scope, or else presents itself there under totally different forms. 



" The greatest importance, however, is to be attached to the total 

 absence of all polarized light exhibited by the two minerals as occur- 

 ring in the meteorites. The contained forms and structures do not 

 polarize the light at all, or only very feebly, although the same 

 minerals, under ordinary circumstances, polarize light very strongly. 

 The absence of all aggregate polarization is especially noticeable, as 

 proving that these objects are not aggregates of crystals. 



" Should we still feel inclined to regard the enclosures as mineral 



