Prof. T. G. Bonney—On some Breccias and Crushed Rocks. 485 
Hyzenas is generally acknowledged, and that no characters can be 
shown to exist by which they can be separated, excepting their size, 
it seems best to follow Prof. Boyd Dawkins, and to regard the Cave 
Hyeena as merely a large variety of the H. crocuta. Consequently, 
as the Hyena teeth from the “ Forest Bed” cannot be distinguished 
from those found in the Caves, they also are regarded as a variety of 
the Hycena crocuta. 
Fortunately there is no doubt in the present instance as to the 
horizon from which these teeth were obtained. ‘The foreman of the 
works, Mr. W. Spurgeon, is positive as to the teeth having been dug 
out of the clay at Corton Cliff, and my colleague, Mr. J. H. Blake, 
who knows the beds of this locality so well, has no doubt as to the 
clay in question being the ‘“ Forest Bed,” and the teeth themselves 
have the colour and mineral condition of fossils from this horizon. 
EXPLANATION OF PLATE X. 
Teeth of Hyena crocuta, Zimm., var. spelea, Goldf., from the “ Forest Bed”’ of 
Corton. All figures natural size. 
Fig. 1. Left upper canine seen from inner side. 
neat was % 5 »» trom outer side. 
5, 2. Right upper premolar 2 from outer side. 
x w. oF Ks an ane enMeresiaey 
ig vot is iy 5) S|) 53) Outer side. 
Nod: 55 59 sph, Os ogee lumer, sides 
aS eee oe 55 ae 4 ee outer side. 
My wae 5 ‘3 »> 4 4) inner side. 
T].—On Some Brecoras AND CRUSHED Rocks. 
By Prof. T. G. Bonney, M.A., F.R.S. 
ROFESSOR HUGHES in a brief but very valuable paper in 
the July Number of this Macazine calls attention to a class 
of breccias of so much importance to the geologist that I am 
tempted to make a summary of notes that have been accumulating 
for some years and present it by way of a supplement. These 
breccias, produced in site by mechanical forces, and subsequently 
modified by chemical, are very liable to mislead the student, and it 
is on this account (having myself been so misled in former, and 
often puzzled in recent years), that I call attention again to the 
subject—of what perhaps sufficient notice is not generally taken in 
text-books of geology. 
“‘Wault rock,” as it is sometimes called, is indeed mentioned, but 
these other breccias, though due to a somewhat similar cause, are rather 
slighted ; yet the latter are of great importance because of their 
resemblance, macroscopic and microscopic, to rocks of a true frag- 
mental origin. . I have not had the opportunity of examining in 
the field the breccia which Prof. Hughes describes, but from speci- 
mens which I have seen and from the circumstances of the case 
have no doubt that he is quite right, and that this St. Davids 
breccia cannot be used as marking an horizon in the granitoid rock. 
Breccias of this kind, to which we might give the names of “ crush 
breccias” (remembering that occasionally they may be due rather to 
