100 «=J. J. Harris Teall—Cheviot Andesites and Porphyrites. 
it more closely allied to the struthious than to any other type of 
bird (vide vol. vii. U. S. Geological Survey of the 40th Parallel, 
Odontornithes). Professor Newton has not failed to notice the 
resemblance between Hesperornis and Colymbus (Encyclo. Brit. 9th 
edit. vol. iii. p. 729, 1875). Professor Marsh thinks it probable that 
this great toothed-bird was descended from a struthious ancestor, 
and that it has left no descendants. That it has so descended seems 
probable; but if it has left no descendants, is it not remarkable 
that it should in many points resemble the recent Colymbus? The 
structure of the palate, the keelless sternum, aborted fore limb, and. 
ostrich-like furm of the scapula and coracoid, are doubtless important 
characters, showing alliance with the Struthionide; but may not 
some of the Carinate have arisen through such a form as Hesperornis ? 
and if so, is it not possible that the recent birds, which show so 
much resemblance to this Cretaceous form, namely, the Colymbide, 
should have descended from this remarkable type ? 
DESCRIPTION OF PLATE III. 
Colymbus septentrionalis from the ‘‘ Mundesley River Bed.”’ 
All figures two-thirds natural size. 
Fic. 1. Right humerus, outer surface. 
Aas Wiha seen from below. ; 
my CD. ,, radius and ulna, from the outer side. The proximal part of the 
ulna is somewhat broken. 
,, 98. Right metacarpals, outer surface. 
Seal) - 5 seen from the radial side. 
eee ,, first phalanx of second finger, outer surface. 
>, 4a a 4 “ radial edge. 
oa ye », femur seen from above. 
SHO iah cas 5, seen from inner side. 
,, 6. Left tibio-tarsus, front view 
NES haa pe 5 view of outer side. 
» 7. Right tarso-metatarsus, front view. 
TIGR ® Fass si view of inner surface. 
II.—Norres on THE CHEVIOT ANDESITES AND PoRPHYRITES. 
By J. J. Harris Tzatz, M.A., F.G.S8. 
LITERATURE. 
Tate, George. The Cheviots, Proceedings of the Berwickshire Naturalists’ Club for 
1867, pp. 359-370. 
Lebour, G. A. Outlines of the Geology of Northumberland, Newcastle-on-Tyne, 
1878. 
Clough, C. T. Notes on the Geology of the Cheviot Hills, Abstracts of the 
- Proceedings of the Geological Society, Dec. 20th, 1882. 
Geikie, James. The Cheviot Hills, ‘‘ Good Words,’’ 1876. 
Winch. Geology of Northumberland and Durham. Trans. Geol. Soc. vol. iv. 
Macroscopic CHARACTERS AND GrEOLOGICAL AGE OF THE CHEVIOT 
ANDESITES AND PORPHYRITES. 
HE Cheviot district is largely composed of those quartzless por- 
phyritic rocks to which the term porphyrite has been applied 
both by English and Continental petrologists. The Cheviot porphy- 
rites are characterized by a compact felsitic’ ground-mass, through- 
1 The term <‘ felsitic’’ is used with exclusive reference to the macroscopic characters 
of the ground-mass. 
