Qrenville A. J. Cole — RhyoUtes of the Vosges. 299 



Fig. 4. Eight lower jaw of Enneodon crassiis, Marsh ; outer view. 



5. Left lower jaw of Menacodon rarns, Marsh ; outer view. 



6. The same jaw ; inner view. 



7. Left lower jaw of Paurodon valens, Marsh ; outer view. 



8. The same jaw; inner view. 



9. Eight lower jaw of Priacodon ferox, Marsh ; inner view. 



a, canine ; b, condyle ; c, coronoid process ; d, angle ; /, dental foramen ; 



g, mylohyoid groove ; s, symphyseal surface. 

 Figures 2 and 3 are twice natural size, and the others three times natural size. 



Tale College, New Haven, March 26, 1887. 



II. — The Rhyolites of Wuenheim, Vosges. 

 By Grenville A. J. Cole, F.G.S., 



Demonstrator of Geology in the Normal School of Science and 

 Eoyal School of Mines. 



IN a paper recently read before the Geological Society,' I ventured 

 the conclusion that the bulk at least of the "pyromerides " of 

 the Continent would be found to be altered lavas of an originally 

 glassy character. The careful drawings and descriptions of various 

 petrographers formed a strong chain of evidence ; and the observa- 

 tions of Mr. T. Davies ^ on materials from Bouley Bay, Jersey, 

 seemed to establish beyond a doubt the connection between rocks 

 authoritatively styled pyromerides and those regarded in this country 

 as ancient rhyolites. Last autumn I visited one of the most typical 

 continental localities, the richly-wooded Tiefenbach valley west of 

 Wuenheim in the Vosges, and a few notes on specimens then 

 collected may possibly be of interest to workers in a similar field. 



It is at once apparent in the steep cliff-like exposure, with old 

 slaty and sandy rocks towards its base, situated just beyond the 

 junction of the roads from Wuenheim and Sulz, that one is dealing, 

 not with a massive " porphyry," but with materials as diverse as 

 those of the famous quarry near the Wrekin. Thus one rock is distinctly 

 banded in tints of grey and yellow-bi'own, and proves under the micro- 

 scope to be a devitrified perlite, an old obsidian rather than a stony 

 rhyolite ; while the " globular " types, made famous, since their dis- 

 covery by M. Koechlin-Schlumberger, through the detailed investi- 

 gations of Delesse,^ occur in considerable variety, as may be seen 

 even in the metal of the neighbouring roads. In some instances the 

 spherulites, 5 millimetres to 1 centimetre in diameter, are purple-red 

 in a yellowish matrix ; in other cases they have a grey and flinty 

 aspect. Many have become chalcedonic in the centre, and may have 

 passed through a hollow stage before this final alteration. Radial 

 structure is visible in the spherulites to the naked eye, and the sur- 

 rounding material is evidently perlitic. 



So much did the spherules at the time of their origin partake of 

 the character of the matrix from which they were derived, that the 

 larger lines of perlitic jointing pass frequently from one into the 



' Quart. Journ. Geol. Soc. vol. xlii. p. 188. 



2 Min. Mag. vol. iii. p. 118. 



^ M.emoires de la Soc. geol. de France, 2me serie, tome iv. p. 308, etc. 



