﻿Mucoids of the Cincinnati Group. 



131 



(Jour. Cin. Soc. Nat. Hist , Vol. I., p. 24), and made to include certain 

 "fucoids" having cylindrical stems with diagonal or longitudinal markings, 

 as if hair-like filaments had been pressed down flat on the stem. The T. 

 venosum was described \>y S. A. Miller, in Jour. Cin. Soc. Nat. Hist., 

 Vol. II., p. 112, and there figured. Dawson, in "Acadian Geology'' (p. 

 27), figures a specimen of what he calls "rill-marks" (Plate VI., figure 4) 

 from the Carboniferous, formed in some such way as can be seen on mud 

 banks now, and Trichophycus venosum is evidently of similar origin. The 

 describer of it says that the plant "consists of a half-cylindrical stem, 

 covered on the cylindrical surface with irregular and inconstant elevated 

 lines," which vary from longitudinal to "diagonally radiating from a cen- 

 tral line." The description of the fossil corresponds so very well with the 

 recent mud mark, that there can scarcely be a doubt as to their having 

 been made in the same way. Another species of the same genus — T. sul- 

 catum (Plate VI., figure 5) — was described by M. and D., in "Contri. to 

 Pal.," No. 2 (p. 4). This is also a fossil rill-mark. For while the surface 

 is longitudinally furrowed, these "furrows are not regular in their size, nor 

 in their course. Sometimes the larger ones are running parallel to each 

 other; at other times several smaller ones intervene." In fact, both figure 

 and description indicate that here again is a fossil with a name which it 

 does not deserve, and which is without question a mark of inorganic- 

 character. 



As long ago as 1852, Prof. James Hall figured in "Pal. of New York/ 

 Vol. II., some fossil remains which he considered as roots or parts of 

 marine plants. Among them (on Plate XL) is a figure of a peculiar 

 dumb-bell fossil. (Plate VI., figure 6a.) This he did not venture to 

 name; but in 1874 Dr. Billings, in "Pal. Foss. of Canada," Vol. II., 

 figured a similar form which he called Arthraria antiquata (Plate XI.. 

 figure 6b), coining the new genus for the reception of the one species. 

 There is no mistaking the form in its resemblance- to that of Prof. Hall s, 

 and there can be no question but that they are both the same. In 1875, 

 in Gin. Quar. Jour. Science, Vol. II., p. 354, Mr. S. A. Miller described 

 a species of Arthraria under the name of A. biclavata. His figure shows 

 perfectly round balls at the ends of a wonderfully symmetrical stem, such 

 as would hardly be found. Still, a great variation is to be detected in the 

 shape and size of different specimens. Some are round, some square, 

 some rough at the ends. (Plate VI., figure 6c.) In many eases all that 

 remains of them is a depression in the rock, the whole substance having 

 been dissolved. Were species to be distinguished on the form alone, every 



