390 Charles Davison — Stone-Rivers, Falkland Islands. 
lens; while the wider posterior flap shows the oblique lines 
described by Messrs. Owen and Fraas. These lines are formed by 
whitish films lying on the rock, which are distinctly striated, and are 
at first sight very suggestive of fin-rays, although it is on the whole 
more probable that they really indicate parallel muscular bundles. 
The axillary region was evidently produced into a well-marked flap, 
or prominence. In proportion te the bony framework the posterior 
flap of integument is much narrower than in the specimen figured 
by Fraas; and since our specimen agrees in this respect with the 
pelvic paddle figured by Owen, it may be assumed that the distal 
extremity of the soft part was produced and pointed as in the latter. 
We have, therefore, now good evidence that while the integuments 
of the paddles of the two primary groups into which the genus 
Ichthyosaurus is divided were of the same general type of structure, 
yet that they differed so markedly in detail as to afford another 
important point of distinction between the two groups. 
I may add that Mr. Montagu Browne has been good enough to 
present the figured half of this interesting specimen to the British 
Museum. 
Ji].—On tue Origin or tHe Stone-Rivers oF THE FALKLAND 
ISLANDS. 
By Cuartzes Davison, M.A., 
Mathematical Master at King Edward’s High School, Birmingham. 
HE stone-rivers of the Falkland Islands have been described by 
Mr. Darwin, Sir Wyville Thomson, Dr. Coppinger, and other 
naturalists who have visited those regions.! The accounts given by 
the two first-named are well-known and easily accessible, and render 
a full description here unnecessary. But it may not be out of place 
to summarise the principal features of the stone-rivers, which must 
find an explanation in any satisfactory theory of their origin. 
They consist of angular blocks of quartzite, “arranged,” according 
to Pernéty, ‘‘as if they had been accumulated carelessly to fill the 
ravines.” The blocks are from two to twenty feet long, and rest 
“irregularly one upon the other, supported in all positions by the 
angles and edges of those beneath” (Thomson). At the same time, 
“they are not thrown together into irregular piles, but are spread 
out into level sheets or great streams ” (Darwin), the surface of one 
visited by Dr. Coppinger being “tolerably flat,” and not indicating 
‘Ca process of accumulation by flow from either side.” The streams 
vary in width from a few hundred feet to a mile or more. Their 
depth is unknown, but, according to Darwin, is probably great: 
though “far down below, under the stones,” says Sir Wyville 
Thomson, ‘‘one can hear the stream of water gurgling which 
1 A. J. Pernéty, Histoire d’un Voyage aux Isles Malouires, etc. (nouy. éd., 
1770, Paris), vol. ii. pp. 1-6; C. Darwin, Journal of Researches, ete. (1879), 
pp. 196-199; Sir C. Wyv. Thomson, The Movement of the Soileap; Nature (Feb. 
22, 1877), vol. xv. pp. 849-360; also, Voyage of the ‘Challenger,’ vol. il. pp. 
245-249 ; and the Ene. Brit., art. on the Falkland Islands; Dr. R. W. Coppinger, 
Cruise of the ‘ Alert’ (1885), pp. 32 33. 
