414 Mr. Bakewellew Lava found on the Sands near Boulogne. 



have belonged to a species not before described, and propose 

 to denominate it Ichthyosaurus coniformis. 



Plate III. 



Fig. 6. (a.) Tooth of the natural size in situ. 



7. do. magnified. 



8. do. transverse section do. 



[For the following note we are indebted to the Rev. Mr, Conybearc. — Edit.] 



" In reference to this paper, Mr. Conybeare observes, that, judging from 

 the data afforded by the present figures, the tooth ascribed to Ichthyosaurus 

 coniformis does not appear to him to differ from those of /. communis suffi- 

 ciently to warrant the establishment of a new species:— the only differences 

 described are a less degree of adnncation in the tooth, and a greater thick- 

 ness in the dental bone ; but as it should appear that Dr. Harlan drew his 

 conclusions from comparison not with other actual specimens, but only with 

 the engravings in the Geological Transactions, some hesitation must be felt 

 in admitting them, especially as the adnncation of the teeth in I. communis 

 is itself very slight ; and the character of their strias is but faintly marked 

 in many impressions of the lithographic plate in the Geological Transactions. 



" Mr. Conybeare wishes, however, merely to postpone the adoption of this 

 new species of Ichthyosaurus until these points can be determined by the 

 comparison of actual specimens, which he hopes to facilitate by transmitting 

 some teeth, &c. of the species previously ascertained, to America. 



" The Snuroccphalus does not yet appear to have been found in England, 

 and forms an important addition to the very interesting class of fossil Sauri." 



LXXII. Lava found on the Sands near Boulogne. By 

 Robert Bakewele, Esq. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



WHEN I was at Boulogne in September last, I was in- 

 formed that masses of lava, of different sizes, were fre- 

 quently found on the sands west of the harbour. M. Dutertre 

 in the lower town had several specimens, from which he 

 obligingly broke one to give me a part. 



The lava is of a darkish gray colour, porous, but extremely 

 hard, and filled with grains of olivine ; it bears a close resem- 

 blance to the lava from the Puy de Nugerre in Auvergne, de- 

 scribed in the second volume of my Travels in the Tarentaise, 

 &c, except that the latter contains no olivine, at least in those 

 parts where I examined it. An inquiry suggests itself of some 

 importance in Geology — Are these masses of lava which are 

 left on the sands after high tides, merely fragments that have 

 been thrown out as ballast somewhere on the coast ? Or are 

 they derived from volcanic rocks hitherto unnoticed in Bri- 

 tanny or Normandy, which, like those of Auvergne, may 



have 



