﻿Fucoids of the Cincinnati Group. 



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sometimes been found burst, and the edges of the aperture torn irregularly. 

 It seems most likely that these so-called fucoids are. in reality, fossilized 

 mud bubbles. All appearances indicate it: and. if so, they can scarcely 

 be considered worthy of generic and specific names. It seems wiser to 

 altogether discard these species and look upon them as ancient relics of 

 gaseous formation of the Silurian age. 



Another sort of a mud mark which has been called a fucoid. is some- 

 times found covering large slabs with long, straight lines, occasionally bulg- 

 ing out in certain spots. Examining the recent mud flats, precisely sim- 

 ilar appearances are seen. (Plate V.. figure 6.) They are caused often 

 by a small stick or stone, or even the body of an insect lodging on the 

 mud. and causing the current to break and flow to each side and depositing 

 a streak of mud behind it. Some of these specimens have been referred 

 to Scolithus linearis (Hall), but erroneously: for this species of Hall's 

 comes under the second head, that of burrows, and it has probably not 

 been found in the Cincinnati group. 



Still another sort of mud mark has been formed in a curious way. 

 Along the edges of streams, on the retiring of the waters of a flood, there are 

 often little shallow pools filled with mudjdy water. The edges of these pools, 

 as they dry. assume irregular shapes, and the mud is often deposited in 

 such a manner as to retain this shape. ('Plate V.. figure 7.) Sometimes 

 it forms an irregular semi-circle, and as the mud in the depression is of a 

 lighter color than that outside, it becomes quite conspicuous. A figure 

 (Plate V., figure 8) is given in "Pal. of Xew York." Vol. II.. Plate 11. 

 very like the one here shown : and Prof. Hall said of the one he figured, 

 that though it had different features than ordinary wave lines, it might be 

 due to inorganic causes. A still more remarkable one, and quite as cer- 

 tainly a mud splash, is in the collection of this Society, and was found near 

 Covington, Ky. It is here shown (Plate V. . figure 9) to compare with the 

 mark of known origin, and comparison is all that is necessary to note the 

 resemblance. 



The washing of water against the bank of a stream often produces rip- 

 ple marks which extend along the shores for some distance in regular, 

 undulating lines. One layer deposited on another to a thickness of several 

 inches gives an appearance like stratification: and. as similar appearance- 

 are presented in some of the rocks of this vicinity, they have been de- 

 scribed as organic under the name of Palwophyrus flexuoua (James). 

 (Plate VI.. figure 1. ) On calling the attention of the deseriber of the 

 fossil to the recent marks, he at once admitted their similarity, and 

 .acquiesced in the suggestion that their origin in eaeh ease was the same. 



