Geological Society of London. 329 



Thecosmilia, namely, T. trichotoma, from the Corallian of Nattheim. 

 He remarked upon the chai'acters of the genus Heterogyra, Keuss, and 

 its allies, including his new genus Phyllogijra ; and further indicated 

 that Thamnastrcea and allied genera have been removed by Milasche- 

 witsch from the Fungidee and placed among the Poritid^, ia con- 

 sequence of their perforated septa, an altei-ation in which he agreed. 

 3. "On the Exploration of two Caves in the Neighbourhood of 

 Tenby." By Ernest L. Jones, Esq. Communicated by Prof. W. 

 Boyd Dawkins, F.E.S., F.G.S. 



The caves noticed in this paper were that of Coygan, near 

 Laugharn, partially described by Dr. Hicks in the Geological 

 Magazine in 1867, and a cave known as Hoyle's Mouth, reported 

 on to the British Association in 1860 by the Rev. Gilbert N. Smith. 

 Both caves were rock-fissures. The Coygan cave had been a Hya3na 

 den, as was shown by the deposits of crushed bones and coprolites 

 trodden down into a solid mass by the passing of the animals. 

 Besides remains of Hyeena, it furnished those of Horse, Mammoth, 

 Tichorhine Rhinoceros, Elk, Red Deer, Roe Deer, Reindeer, Cave 

 Bear, Cave Lion, Bos primigenius, Wolf, and Fox. The presence of 

 Hippopotamus was doubtful. Besides these animals, the presence 

 of PalaBolithic man in the cave was indicated by some cut bones and 

 by two flint-flakes evidently chipped by man. In the second cave, 

 Hoyle's Mouth, the Hyeena, the Cave Bear, etc., were wanting, the 

 place of the latter being taken by the common Brown Bear. In one 

 part remains of an old hearth were found ; and the whole contents 

 of the fissure pointed to a Neolithic date. At one time the cave 

 appears to have been used as a place of sepulture. 



4. "Note on the Comparative Specific Gravities of Molten and 

 Solidified Vesuvian Lavas." By H. J. Johnston-Lavis, Esq., F.G.S. 

 From some experiments made on Vesuvian lava, Prof. Palmieri 

 in 1875 expressed the opinion that its specific gravity, when 

 molten, might be as high as 5-0, though when cooled it is only 

 2-7. The author described the results of experiments made in 

 December, 1881, on some lava flowing across the Atrio del Cavallo. 

 Favoui-able circumstances enabled him to gain a position above a 

 perfectly molten stream, the surface of which was protected from 

 radiation by the heated walls of a tunnel which the lava had already 

 formed by cooling of the crust. On to this were dropped, from a 

 height of 1-| yard, (a) light scoria ; this floated on the surface until 

 lost to view (the stream could be watched for 160 yards or so) ; (b) 

 fairly solid lava, with some vesicular cavities : this slowly sank, 

 until after some distance it disappeared ; (c) the most compact lava 

 that could be found, in which, however, were a few small cavities : 

 this sank rapidly, the molten rock welling up round it. The author 

 considered that these experiments demonstrate that the cooled lava 

 is more dense than the molten, and that the apparently contradictory 

 results obtained by Prof. Palmieri were due to the fact that the 

 surface of the stream, by loss of heat, had become viscid, so that 

 the solid material floated, though of greater density. The author 

 concluded by citing other confirmatory evidence of his view. 



