566 Notices of Memoirs — W. Dames on ArchcBOj)teryx. 



unaltered rocks, which we have thus recently discovered, stand 

 related to the remarkable breccias and boulder beds of the Permian: 

 and Trias of the Birmingham neighbourhood, is not yet fully worked 

 out. That they are overlain upon their flanks by representatives of 

 all the subformations of the Silurian, as developed upon the 

 Malverns, has recently been determined by the author and his 

 students. That from these local ridges (many of which are now 

 buried from sight by more recent accumulations), and not from 

 distant Welsh rocks, the supposed Permian glacial boulders might 

 originally have been derived, may now be suspected, and one of the 

 most vital difficulties in the interpretation of the rocky structure 

 of the district will thus disappear from sight. That they afforded 

 the majority of the innumerable quartzite pebbles found in the 

 boulder-beds of the Trias of the Midlands is even more probable, and 

 thus another and even more important fact becomes naturally 

 accounted for. 



On the Steuctuke of the Head of Aech^opteeyx. By W. 



Dames. ^ 



fllHE ArcJiceoptenjx in the possession of the Royal Mineralogical 

 JL Museum of this kingdom [Prussia] will be made the subject 

 of a detailed description accompanied by figures. By uncovering 

 some bones hitherto imbedded in matrix, a better knowledge has 

 been gained of the structure of the head. When the specimen was 

 acquired for this collection, the skull showed on its exposed right 

 side two large apertures. The posterior hole, situate under the roof 

 of the skull, was easily identified as the orbit of the eye ; a view 

 the more evident since the cavity contains a well-preserved sclerotic 

 ring, which is formed of a single row of overlapping scale-like, bony 

 plates, as in so many living birds. The anterior edge of this eye- 

 cavity is formed by a small bone, which, turning somewhat back- 

 wards, reaches to the base of the skull. This bone is now regarded 

 as the lachrymal. It forms the hinder boundary of a second aperture 

 which is large and of rounded triangular form. In the middle of 

 this cavity lies a crushed fragment of bone which has no natural 

 connexion with the adjacent parts of the skull. This aperture has 

 been determined as the nasal cavity by Yogt and Marsh, in their 

 accounts of the head of Arcliceopteryx. The specimen, however, 

 shows that the anterior part of the skull then laid imbedded in the 

 rock, and the contaur of the head has only been shown by carefully 

 clearing away the matrix. This development yields the remarkable 

 result that in front of the opening hitherto considered nasal, lies a 

 third opening which is 9mm. long, of sharp elliptical form and 

 placed oblique to the long axis of the skull. It is separated pos- 

 teriorly from the middle opening by a small bony bridge. It is 



1 Communicated by Hen- Ewald, 27 July, 1882, to the Berlin Academy. Trans- 

 lated by Professor H. Gr. Seeley from a separate copy, extracted from the 

 Sitzung&berichte, vol. zxxviii. p. 817. 1882. 



