X] ARCHAEOCALAMITES. 383 



belonging to the sub-genus Galamitina, which measures about 

 2 m. in length and 23 cm. in breadth, with 86 nodes. In the 

 Natural History Museum, Paris, there is a cast nearly 2 metres 

 long and more than 20 cm. wide, which is referred to the sub- 

 genus Galamodendron. 



V. Archaeocalamites. 



In the Upper Devonian and Culm rocks casts of a well- 

 defined Calamitean plant are characteristic fossils ; stems, leaf- 

 bearing branches, roots and cones have been described by several 

 authors, and the genus Archaeocalamites has been instituted 

 for their reception. Although this genus agrees in certain 

 respects with Calamites, and as recent work has shown this 

 agreement extends to internal structure, it has been the 

 custom to regard the Lower Carboniferous and Devonian plants 

 as generically distinct. The surface features of the stem-casts, 

 the form of the leaves, and apparently the cones, possess certain 

 distinctive characters which would seem to justify the retention 

 of a separate generic designation. 



We may briefly suminarise the characteristics of the genus 

 as follows : — 



Pith-casts articulated, with very slightly constricted nodes ; 

 the intemodes traversed by longitudinal ribs slightly elevated 

 or almost flat, separated by shallow grooves. The ribs and 

 grooves are continuous from one internode to another, and do 

 not usually show the characteristic alternation of Calamites^. 

 Along the nodal line there are occasionally found short longi- 

 tudinal depressions, probably marking the points of origin of 

 outgoing bundles. Branches were given off from the nodes 

 without any regular order ; a pith-cast may have branch-scars 

 on many of the nodes, or there may be no trace of branches 

 on casts consisting of several nodes. The leaves ^ are in whorls ; 

 in some cases they occur as free, linear, lanceolate leaves, or on 

 younger branches they are long, filiform and repeatedly forked. 



1 Vide Stur (75), etc. for remarks on the course of the vascular strands. 



2 For good figures of the leaves vide Stur (75), Eothpletz (80), Ettings- 

 hausen (66), Solms (96). 



