DISTRIBUTION FRANCE AND ITALY 599 



crinoid remains. In places among the pillows there are continuous 

 masses of limestone with dimensions up to 30 by 60 centimeters. 



Reuning ascribes the origin of the pillows to a violent submarine erup- 

 tion. The lava, boiling up with great force and coming into immediate 

 contact with the water, was rent asunder and became balled-up into the 

 various spheroidal, ellipsoidal, and roll-like forms, which cooled quickly 

 and settled down irregailarly on one another. The larger limestone 

 masses were thought to have been brought up from the depths with the 

 eruption, or else the lava masses sank into a soft, limy ooze and inclosed 

 it among themselves. Several of Eeuning's plates show excellent exam- 

 ples of pillow structure, and one of them shows a large cross-section of a 

 pillow with radial jointing. 



FRANCE AND ITALY 



Mazzuoli and IsseP^ have described from the eastern coast of Liguria a 

 dense basic rock with a kidne3^-shaped nodular structure, the masses being 

 10 to 15 centimeters in diameter and having variolitic surfaces and con- 

 centric internal structure consisting of bands of different color and hard- 

 ness. These are arranged like the elements of a pudding in a paste for 

 the most part epidotic. The masses are called concretionary C^arnione 

 di concentrazione"). 



Cole and Gregory-^ described the porphyritic and variolitic diabase of 

 Mont Genevre, on the French-Italian border, as a rock "which weathers 

 into great rounded spheroids, the faces of which appear to be surfaces of 

 cooling, since the masses are often jointed within into radial prisms." 

 These masses resemble pillows and soft cushions piled on and pressed 

 against one another, so that each cliff shows a number of swelling sur- 

 faces and curving lines of junction. There are small vesicles in the rock, 

 especially toward the surfaces of the masses, and in places the whole rock 

 is vesicular and slaggy. A layer of variolite, from 1 to 7 or 8 centimeters 

 thick, believed to be a devitrified tachylite, forms the outer crusts, the 

 varioles of which are drawn out parallel to -the surface and range from 

 almost microscopic to 5 centimeters in diameter. 



"It is possible tliat tlie surfaces of ordinary spheroids of contraction, even 

 in tlie heart of a cooling mass, may differ appreciably from the more central 

 portions and, consolidating more rapidly, exhibit a vitreous structure. . . . 

 But we prefer to read in the irregular shape and involuted surfaces of the 



i» L. Mazzuoli and A. Issel : Relazione degli stude fatti per un relievo delle masse 

 ofiolitiche nelle riviera di Levante (Liguria). Boll. R. Comit. Geol. d'ltalia, vol. xii, 

 1881, pp. 313-349. 



2" G. A. J. Cole and J. W. Gregory : The variolitic rocks of Mont Genfevre. Quar. Jour. 

 Geol. Soc. London, vol. 46, 1890, pp. 295-332. 



