REPORT OP THE STATE PALEONTOLOGIST 1901 597 



placed by iron oxids. The rock is arenaceous and any expression 

 of the structure is more or less obliterated by the coarse granular 

 texture of the matrix and residue. In the lower portion of the 

 segments this residue is obscurely marked in places, specially 

 near the axis, by irregular longitudinal lines or striae; but neither 

 these nor the rather indefinite strand seem to present a distinctly 

 vascular aspect. The characters of the residue more strongly 

 suggest the modified or pseudocompound structure of the more 

 complicately organized algae, as in the stems of certain of the 

 Phaeophyceae, rather than the vascular bundles or vessels of a 

 fern. 



Whether the fronds of Thamnocladus were borne on stipes 

 is indeterminable from the material in hand, as is also the 

 nature of the reproductive organs. 



The distinction of Thamnocladus clarkei from other 

 Paleozoic algoid forms from this country would seem a matter of 

 little difficulty, as there are but few species which the plant in 

 hand at all closely resembles. Buthotrephis gracilis 

 Hall,-"^ from the Trenton, is slender, flexuous, and slightly sug- 

 gests the Meshoppen specimens, but the ramules are irregularly 

 fasciculate, sometimes dilated upward, and generally as narrow 

 near the base as at the top. B. s u b n o d o s a Hall^ is also 

 fasciculate. The aspect of f asciculation in Thamnocladus 

 clarkei shown on pi. 3 and 4, is due to superposition, and is 

 not a feature of the ramification. Even in these portions the 

 central strand is generally visible in Thamnocladus. The 

 fragment figured by Salter^ as a " dichotomous rootlet " is some- 

 what suggestive of the American plant, though it is more rigid, 

 narrow and distantly branching like some of the more slender 

 examples referred to Psilophyton in America. 



Thamnocladus is distinguished from Psilophyton by its lax, 

 flexuous, dichotomous, bushy habit, the rounded or flattened 



^ Pal. N. Y. 1847. 1: 62, pi. 21, fig. 1. 



* 1:262, pi. 68, fig. 3. This species is generally indistinguishable by 



any described characters from the group known in Europe as Palaeochon- 

 drites. 



" Quar. jour. geol. soc 1858. v. 14, pi. 5, fig. 3. 



