Geological Society. 71 



Similarly, sodium will decompose the oxides of carbon, while carbon 

 will decompose oxide of sodium; and just as a sufficient excess of 

 chlorine may be made to effect the almost complete decomposition 

 of a given quantity of water, so may a sufficient excess of carbon (or 

 carbonous oxide) be made to effect the almost complete decomposition 

 of a given quantity of sodium-oxide or zinc-oxide, as in the ordinary 

 processes for obtaining the two metals, notwithstanding that, for 

 an equal consumption of oxygen, the respective combination heats 

 of sodium and zinc exceed by far the combination heat of carbon or 

 carbonous oxide. 



Again, although the combination heat of oxygen and carbonous 

 oxide is 68 units, while that of oxygen and hydrogen is only 57 

 units, yet, as was shown by Bunsen many years ago, upon exploding 

 a mixture of oxygen with a joint excess of carbonous oxide and hy- 

 drogen, the oxygen does not attach itself exclusively to the carbonous 

 oxide, but divides itself between the carbonous oxide and hydrogen 

 in a ratio determined by their relative proportions. 



GEOLOGICAL SOCIETY. 

 [Continued from vol. xxxv. p. 399.] 

 March 25th, 1868.— Prof. T. H. Huxley, LL.D., F.R.S., President, 

 in the Chair. 



The following communications were read : — 



1. "On some new species of Palaeozoic Crustacea from the 

 Upper Silurian rocks of Lanarkshire, &c, and further Observations 

 on the Structure of Pterygotus." By Henry Woodward, Esq., 

 F.G.S., F.Z.S. 



The nature of the remains which have been referred by Mr. 

 Salter to Eurypterus {Pterygotus) punctatus was first discussed by 

 the author, who came to the conclusion that the Lanarkshire spe- 

 cimens belong to a new species — Eurypterus scorpioides, — while the 

 chelate antennas and the detached lip- plate must have belonged to 

 other species. 



Eurypterus scorpioides is the first of the new forms now described 

 by Mr. Woodward, and is represented by a specimen exhibiting an 

 almost entire individual, and certain other fragments. The punc- 

 tate ornamentation of this species may be readily distinguished from 

 the scale-like markings of Pterygotus and Slimonia. The second new 

 form, Eurypterus obesus, is remarkable for the great obesity of the 

 thoracic somites ; it is represented by the impression and counter- 

 part of an entire specimen. Its small size suggested to the author 

 the possibility of its being the young of some larger species. The 

 third new species, Pterygotus raniceps, is at present known only by 

 a single example ; its head is remarkable on account of its obtusely 

 pointed triangular form and prominent marginal eyes. 



In conclusion the author made some observations on the structure 

 of Pterygotus^ showing that it possessed a series of branchial plates 

 — leaf-like bodies presenting a highly vascular and delicate struc- 



