392 A. Smith Woodward — On Poecilia from Oeningen. 



but does not appear to, be spliene ; and a speck or two apparently 

 of thorite." From the microscopic sections in my possession it 

 seems to be a biotite gneiss consisting of orthoclase, microcline, and 

 plagioclase, quartz, and biotite. A bright yellow epidote is very 

 abundant in needle-like crystals which radiate from the iron ores 

 and the mica, and form nests and strings running through the rock. 

 Orthite is present in fair amount in large crystals, which are 

 rounded and without trace of crystalline form, but here and there 

 have parallel faces and a straight extinction, showing that the ortho- 

 axis is the direction of elongation. In one or two crystals it is 

 zonal, and an indistinct cleavage is to be made out. In convergent 

 light it is widely biaxial and of negative sign. Its colour is brown, 

 more intense than in the Fell Hill granite, and the pleochroism 

 more marked, being — 



7, deep greenish brown. 

 y8, dark yellow brown. 

 a, paler yellow brown. 

 Absorption : 7 7 /3 7" a. 



Twinning and parallel growths with epidote were not observed. 



Professor Heddle's opinion was that this is not a Scottish rock, 

 and the microscopic evidence goes to support this view, for while 

 similar rocks have not been described from Scotland they are 

 well known in Sweden and Norway. A glance at the inap given 

 by Messrs. Peach and Home in their paper on the Glaciation of the 

 Orkney Islands^ shows how close, in their opinion, the Norwegian 

 and Swedish ice came to the Orkneys. In the south and west of 

 the group they found many rocks in the Boulder-clay to which 

 they could confidently ascribe a Scottish origin. It is in accordance 

 with all we know about the glaciation of the Orkneys to believe 

 that, at certain times at any rate, the north-east corner of the 

 archipelago was overridden by Norwegian ice, and that this boulder 

 is of Scandinavian derivation. 



III. — On a supposed Tropical American Fish (Poecilia^ from 

 THE Upper Miocene op Oeningen, Baden. 



By Arthur Smith "Woodward, F.L.S., F.G.S. 



N 1861,'- the late Dr. T. C. Winkler, of Haarlem, published 

 a memoir on some fishes from the well-known Upper Miocene 

 fresh-water formation of Oeningen, and among other new forms he 

 believed he could recognize an extinct species of the Cyprinodont 

 genus, Poecilia. This peculiar fish not being known elsewhere 

 beyond the fresh waters of tropical America, the determination 

 of a Miocene representative in a European fresh-water deposit 

 excited some interest both among geologists and ichthyologists ; and 

 the occurrence of Poecilia oeningensis in Baden has been almost 



^ Quart. Joiirn. Geol. Soc, xxxvi, pi. xxvii. 



^ T. C. Winkler, "Description de quelques Nouvelles Especes de Poissons 

 Fossiles des Calcaires d'Eau Douce d'Ueningeu " (Haarlem, 1861J. 



