PTIOCEEDTNOS OE GEOLOQICA.L SOCIETIES. 



31 



Restoration of Pteraspis. 



My dear Sir, — Mr. Lankester, in referring in your last number to a 

 paper of mine, in your November number, lias given us two sketches of 

 specimens of Pteraspis and the restoration of the test by Professor Huxley. 

 Substantially, in the diagram of Professor Huxley, and in my second 

 figure, \vc have the same elements ; and with my other figures Mr. Lan- 

 kestcr does not interfere. I do not think, however, that his specimens are 

 so decisive as he implies they are. In his first sketch there is no decided 

 appearance of the central ridge or prolongation, and it appears to me, that 

 there is a much larger portion of the test posterior to the cornua than what 

 is to be discovered in the restoration of Professor Huxley. In his second 

 sketch or specimen, I cannot see any certain evidence of the cornua at all, 

 and therefore, from it also, I cannot gather how the spine or central pro- 

 longation of the shield is related to them. Mr. Lankester informs your 

 readers of first-rate specimens having been in the museums and in private 

 collections for some years. Perhaps some of these may throw light on this 

 point, and on other points connected with Pteraspis. 



Meantime, believe me, my dear Sir., 



Yours truly, 



Craifff Dec. 8. Hugh Mitchell. 



PROCEEDINGS OF GEOLOGICAL SOCIETIES. 



Geological Society. — November 19th. — " On the Cambrian and Huro- 

 nian Formations, with remarks on the Laurentian." By J. J. Bigsby, M. D. 

 The author came to the conclusion that the Cambrian and the Huronian 

 arc distinct formations, and the latter is very much tne older. 



December 3rd, 18G2. — L " Description of the Ilemains of a new Enalio- 

 Bau 'ian {JEosanrus A.cadiunus), from the Coal Formation of Nova Scotia." 

 By O. C. Marsh, Esq., M.A. Communicated by Sir C. Lyell, V.P.G.S. 



2. "I description of Anthracosaurus, a new genus of Carboniferous Laby- 

 rinthodonts." By Professor T- H. Huxley, F.R.S., F.G.S. 



Anthracosaurus is distinguished from all other known Lab3^rinthodonts 

 by the quadrate form and oblique position of the orbits, by the existence 

 of elongated supratemporal foramina, and by the comparatively small 

 number and large size of the teeth. The skull exhibited had an extreme 

 length of 15 inches, and an extreme width of 12 inches. There are about 

 30 maxillary, 2 vomerine, and 10 palatine teeth, which arc ridged, and be- 

 come flattened and two-edged towards their apices. The vomerine, pala- 

 tine, and some of the anterior maxillary teeth are between 2 and 3 inches 

 long, and from \ to f- of an inch in diameter at the base. The species ex- 

 hibited was named A. Russelli, after its discoverer. Probably its entire 

 skeleton had a length of not less than (5 feet. 



3. "On the thickness of the Pampean Formation near Buenos Ayres." 

 By Charles Darwin. Esq., M.A.. F.B.S., F.G.S. 



Some sections of Artesian wells sunk in this formation showed its entire 

 thickness near Buenos Ayres to be about 210 feet. It was stated to rest 

 upon various marine beds upwards of 100 feet thick, containing Ostrea 

 Ratagonica, Ostrea Alvarezii, Pecten Paranensis, etc. These reposed 

 upon red calcareous clay, which was bored through to a depth of 213 feet 

 more, contained no fossils, and is of unknown age. 



