302 



DR. J. W. DAWSON ON NEW 



4. Lepidodendeon peim^vttm, "Rogers. (PL XII. fig. 13.) 



Mr. Wright's collection contains fragments of a Lepidodendron 

 from Milo, New York, which seems to belong to the species above 

 named, but presents the curious peculiarity of having the leaf-bases 

 depressed instead of being prominent. This may result either from 

 some peculiarity of pressure or from the leaf-bases being deciduous 

 and leaving depressed scars when removed. In either case these 

 specimens illustrate this peculiarity as seen in the Lower Silurian 

 Glyptodendron of Claypole, which may possibly have had decorti- 

 cated leaf-bases. Specimens of this kind, of course, retain no distinct 

 vascular marks, and the impression on the matrix resembles those 

 decorticated Lepidodendra of the Coal-formation which used to be 

 named Lyginodendron, but which, in Nova Scotia at least, usually 

 belong to the species Lepidodendron rimosum. 



5. Cellttloxylon peim^vtth, gen. & sp. n. 



A silicified trunk, showing in cross section large and somewhat 

 unequal hexagonal cells, with an appearance of lines of growth 

 caused by concentric bands of smaller cells. No medullary rays. 

 The longitudinal section shows either cells superimposed in vertical 

 rows, or a sort of banded prosenchymatous tissue; but the structure 

 is much masked by the crystallization of the quartz. 



This specimen is from the collection of Prof. J. M. Clarke, of Am- 

 herst, Massachusetts, and was obtained from the Hamilton (Middle 

 Erian) of Canandargua, New York. It was undoubtedly a woody 

 stem and not an Alga ; but its structure is even less specialized than 

 that of Prototaocites, from which it differs in the want of medullary 

 rays, and in its less distinctly elongated wood-cells without spiral 

 markings. It has some resemblance to Aphyllum paradoxum of 

 Unger, but is more uniform in its structure. It adds another to 

 those mysterious woody stems of doubtful affinities which, in the 

 Devonian or Erian of both sides of the Atlantic, represent the 

 Taxinese and Conifers of later formations. 



Additional specimens received from Prof. Clarke show that the 

 appearance of rings of growth is caused by large cells disposed in 

 concentric narrow bands between the wider bands of fine fibrous 

 tissue. In the longitudinal section these bands of large cells appear 

 to be parenchymatous and not vascular. There are no medullary 

 rays, but rounded patches of cellular tissue appear here and there 

 in the fibrous layers. The structure is thus very peculiar, and ap- 

 pears to have been the result of a kind of exogenous growth, in which 

 coarse parenchymatous layers were deposited between the periodical 

 rings of the stem, reminding one of the bark-like layers interposed 

 between the growth-rings in Gnetum and in some tropical climbers. 

 The stem of the present plant was, however, in all probability, of 

 much more simple character, though woody and capable of resisting 

 pressure. It is to be observed also that the specimens neither show 

 the structure of the pith or bark, and that the finer structures of 

 the tissues preserved must have been partially obliterated by the 



