PRB-CARBONIFEROUS PLANTS. 



89 



unusual feature of being leafy, so that fragments might have been referred 

 to the genus Lycopodites. The leaves were, however, precisely of the 

 same character with those of P. princeps, and their ligid spine-like nature 

 was well shown by their projecting downward and upward into the stone 

 from flattened stems. After the removal of the leaves, the stems exhibited 

 rounded spots, somewhat irregularly arranged, indicating the slender 

 bundles of vessels passing to each leaf Being flattened the stems were 

 more smooth than usual. No fructification was observed, and the circinate 

 termination of many of the branches indicated that the plants were 

 immature. 



In detached hand specimens I have no doubt that these plants would be 

 regarded as specifically, perhaps generically, distinct from P. princepa ; 

 but the comparison of large numbers of nearly entire specimens forbids 

 this conclusion, by showing such links of connection as render it impossible 

 to draw any decided line of separation. The present form must be 

 regarded as merely varietal, or possibly as the normal state of the imma- 

 ture or barren plants. To indicate the points of diflFerence, however, I 

 have given the varietal name ornatam. 



Specimens referrible to this form, and showing internal structure, present 

 no difference of appearance as compared with the ordinary type of 

 princepa. 



> t 



49. PsiLOPHyTON ROBUSTius, Dn.— (PL XI, Figs. 130 to 132. PI. XII. 

 PI. X, Fig. 121.)— L. D., M. D., Upper Silurian, Gaspd. 



Stems stout, smooth or slightly furrowed longitudinally, and usually dotted 

 with small irregular spots marking the position of ramenta or 

 rudimentary leaves. Main stems branching irregularly and 

 finally dichotomous. Rhizomata similar to those of the last 

 species, but apparently smoother and less massive. Internal 

 structure as in last species, but with a thicker vascular axis, the 

 vessels having a tendency to arrangement in radiating series. 

 Fructification in clusters of naked spore-cases, acuminate and 

 somewhat falcate, borne on short dichotomous pedicels. 



This species was merely indicated in former papers on the evidence of 

 a few fragments. The discovery of a bed richly stored with the stems in 

 situ, and bearing fructification, enables me now to complete its descrip- 

 tion. The habit of growth at once distinguishes this species, as well as 

 its smooth and dotted surface, the abseuce of distinct leaves and its 

 crowded clusters of spore-cases. Its internal structure also, though of the 

 same general type, is notably different. It appears to have grown under 



