100 G. Poulett Scrope — On Lavas. 



of these papers was read before the Geological Society on the 24th 

 of November, 1869, and appears in the February Number of the 

 Society's Journal. (See Gbol. Mag. January, 1870, p. 36.) 



Professor Owen is opposed to the union of Birds and Eeptiles, 

 and points to their affinity with the Implacental Mammals, in the 

 development of the embryo, in the brain, in the circulating system, 

 etc. He strongly combats the inference that warm blood is an 

 essential accompaniment of an animal endowed with the power of 

 flight, and cites the cockchafer as an instance of a living creature 

 capable of powerful flight, whose body, nevertheless, only raises 

 the thermometer one degree above the surrounding medium. He 

 maintains that the constant accompaniment of hot-bloodedness is a 

 non-conducting covering to the body, and that we may with cer- 

 tainty infer that ArchcBopteryx was hot-hlooded, because it had 

 feathers, not because it could fly. We think a happier illustration 

 than the cockchafer (so dissimilar in bulk and organization from the 

 Pterodactyle) is that of the shark and porpoise — the former cold- 

 blooded, the latter warm-blooded — both peiforming the same mus- 

 cular feats, in following a ship for days, with equal ease. (See Prof. 

 Owen's Monograph, p. 73.) 



Space does not admit of our pursuing this interesting subject, but 

 we have said enough, we trust, to show that, taking a single Mono- 

 graph out of the present fasciculus, forming Vol. XXIIL, there is 

 garnered a rich store of palseontological matter for those who care 

 to benefit by the works of this useful Society. 



EXPLANATION OF PLATE IV. 

 Fig. 1. Bimorphodon macronyx, Owen (|- original). Restoration, copied from Prof. 



Owen's Monograph in Pal. Soc. 1870, vol. xxiii., pi. 20. 

 Fig. 2. Probable outline of integument (greatly reduced in size). 

 Fig. 3. Four of the tail vertebrae of the natural size, showing the fine parallel bony 



fibres which strengthen and render rigid the slender joints. 

 Fig. 4. Foot of Rhamphorhynclms (| nat. size) placed, for comparison, with hind 



limb of Bimorphodon^ also copied from Prof. Owen's plate. 

 Fig. 5. Side view of skull of Eeeent Saurian {Lyriocephalus). 



n. — On the Chakacter and Composition of Lavas. 

 By G. Poulett Scrope, F.R.S., F.G.S., etc. 



I HAVE been gratified by observing of late the appearance among 

 geologists of a more general appreciation of the study of vol- 

 canic phenomena, — using that word in its broadest sense, as com- 

 prehending not merely the occasional outbursts of vapour, ashes, 

 and lava, but also the action of those subterranean forces, to which 

 alone we are indebted for the existence, now or in former times, of 

 , any dry land whatever above the dead sea-level at which the agents 

 of denudation would otherwise maintain the surface of the globe. . 

 Perhaps the tendency of recent writers on this subject has been 

 rather to indulge their imaginations by theorizing on the possible 

 nature of the interior of the earth, than to examine carefully the 

 facts observable on its surface. I venture, therefore, to recal those 

 who show this inclination to wander from the legitimate path of in- 



