260 PROF. W. C. WILLIAMSON ON THE 



reconnu que les Catamites cannaformis et varians vont avec 

 les Asterophyllites du type EquisetiformeSj SchL^ et les 

 Volhnannia gracilis ) Vv., que le moule des tiges de ces vege- 

 taux est rempreint de la structure du bois d' Arthropitus •/' 

 and in a private letter to myself, that eminent geologist 

 says, " Comme vous, j^ai reconnu que le bois d' Arthropitus 

 appartient aux Calamites du type C. cannceformis." Since 

 tlie contrary idea prevailing in the French school of palae- 

 ontologists has chiefly rested, of late years, upon the dis- 

 coveries of M. Grand^Eury himself, I presume we shall 

 now hear no more of that mistaken hypothesis. 



The identity of Calamites and Arthropitus being thus 

 established, the latter genus disappears ; but there yet 

 remains for consideration the relationship subsisting 

 between Calamites and Calamodendron, regarding the 

 latter genus as identical with the Calamitea of Cotta. 



On this point, I think, some light is thrown by a study 

 of the plant which I described in 1869^, under the pro- 

 visional name of Calamopitus. The figures in the accom- 

 panying Plates will facilitate an apprehension of what 

 I propose saying on this subject. 



Fig, I represents an ordinary form of a fossil Cala- 

 mite, with its transverse nodal constrictions, a, and its 

 longitudinal internodal ridges and furrows, b. When 

 covered with a very thin film of coal moulded upon the 

 contours of figure i, this form represents the ordinary 

 Equisetiform Calamite of the Brongniartian school. But 

 all parties now see in such a specimen something more. 

 I long ago pointed out that these fossils were merely the 

 inorganic casts of the fistular medulla of a Calamite, 

 in which a nodal medullary septum extended more or 

 less completely across the medullary cavity at each node, 

 and to the presence of which the transverse constrictions 



* Trans. Lit. and Phil. Soc. Manchester, 3rd ser, vol. iy. Session 1868-9. 



