A. L. Du Toit—Pinpe- Amyydaloids. 15. 
it. He says:! ‘A peine le sable volcanique est-il emporté de quelque 
endroit immédiatement voisin des cénes que déja, le basalte ancien des 
plateaux apparait, dans sa position primitive, sans avoir éprouvé, par 
suite des éruptions le moindre déplacement. C’est pour cela que nous 
croyons que les cones se sont formés autour de petits tubes, ou 
cheminées, et non sur une fracture continue.” With regard to the 
No. i lava-stream he says:? ‘‘ L’observation du terrain semble établir 
que, dans la formation du malpays le plus étendu et le plus ancien, 
ont participé des laves qui sortaient simultanément, des quatre bouches 
et qui, dans leur course, se sont fondues au point de ne plus constituer 
qu’un seul gateau.” 
With all deference to Mr. Ordéiiez I venture to tentatively suggest 
the following hypothesis. We may have here a most interesting 
example of the transition from fissure eruptions to crater eruptions. 
The lava-streams Nos. i and ii, each of which, as I understand him, 
cannot be separated into portions according to the vents which gave 
rise to them, may well have both issued from a fissure. This fissure 
being partially obstructed may then have retained four openings 
through which the fragmental materials of the four cones were ejected. 
Finally, the vent of the main cone alone remained open and gave rise 
to the last two lava-streams. 
EXPLANATION OF PLATE II. 
DEscRIPTION OF PHOTOGRAPHS. 
Fig. 1, Jorullo. Figs. 2 and 3, Nevado de Toluca. 
Fic. 1.—View of Jorullo from the magnetic west, showing its wooded slopes, the 
latest, No. iv, lava-stream issuing from the cone high up on the left, and in 
the foreground the park-like vegetation on the No. 1 lava-stream. 
Fic. 2.—-View of the crater of Nevado de Toluca. The bridle-path leading down 
into the crater on the right, a part of the Laguna Chica with the central 
lava dome immediately behind it, and behind the dome the interior slopes 
covered with screes; and on the lett the Pico del Fraile, or highest poimt 
of the crater rim. 
Fie. 3.—View of the crater of Nevado de Toluca looking N.E. from high up on 
the S.W. crater rim. In the centre the Laguna Grande with the lava dome 
on the right, and in the right foreground part of a scree with patches of 
snow. 
LV.—Prrz-AMYGDALOIDS. 
By A. L. Du Torr, B.A., F.G.S., Geological Survey of Cape Colony.® 
IPE-AMYGDALOIDS, although recorded in the Deccan Traps of 
India and in Tertiary Basalts from Mull, are rather uncommon 
rocks except in South Africa. They were described by Professor 
E. Cohen, who obtained his specimens through Mr. J. Orpen from 
the Stormberg lavas (Lower Jurassic) of Basutoland, a formation in 
which they are very abundant. Since then they have been found 
1 Loe. cit., p. 28. 
2 Loe. cit., p. 41. 
3 With the permission of the Geological Commission. 
4 Cohen, ‘‘ Ueber einige eigenthiimliche Melaphyr-Mandelsteine aus Siid-Afrika 
Neues Jahrbuch, 1875, p. 113. ,‘‘ Mandelstein aus den Maluti-Bergen,Stid-Afrika ” > 
ibid., 1880, pp. 1, 96. 
