﻿Fucoids of the Cincinnati Group. 



163 



Genus Dystactophycus, M. & D. 1878. 



In Contributions to Palceontology, No. 2, pp. 2 and 3, Miller and Dyer 

 established the genus Dystactophycus for the reception of certain fos- 

 sils supposed to be plants, and consisting of rhizomes of fronds "mam- 

 miform or depressed conical," with the "surface marked by numerous 

 closely-arranged concentric ridges or wrinkles." One species (D. mam- 

 millanuni) was described and figured, and the generic description answered 

 for the specific. It was supposed to be elevated above the surface of the 

 rock one and a half inches; there was no appearance of any branch spring- 

 ing from the apex, and the whole "plant" consisted of this concentrically 

 wrinkled frond, elevated in the center. 



From the rocks of the Niagara group, Professor Hall has described a 

 coral which has long been known as Lichenalia concentrica. It can now 

 be conclusively shown that certain species of Monticulipora have bases 

 which are marked with concentric lines very similar to those of Lichenalia 

 concentrica, and there can hardly be a doubt but that they are the same. 

 A figure of Hall's species is given in the Palceontology of New York, Vol. 

 II., Plate 40E, which exactly resembles the markings of the Dystactophy- 

 cus. This "fucoid," then, has resulted from the impression of the base of 

 a coral resting on a mud-bank and leaving its mark in the concentric 

 rings The elevated portion is the part extending up into the base of the 

 coral stem, and the outer rings mark the extent of the expanded base. 

 Comparison of Hall's figure and specimens of Dystactophycus leave little 

 doubt as to this fact. 



Another and yet more striking impression has also been described as a 

 fucoid under the 



Genus Heliophyctjs, M. & D. 1878. 



This is in Contributions to Palaeontology No.2, and H. stelliforme is the only 

 species. It has a "star-like frond, without any stem or evidence of attach- 

 ment," with five rays, each one apparently round and tapering to a point. 

 "They were evidently flexuous," and had rugose markings on the surface — 

 the lines near the body "forming an angle in the middle, and bending forward 

 down the side ; farther from the body the lines become arcuate on top, 

 while toward the points of the shoots [rays] the lines are somewhat irreg- 

 ularly transverse." It seems quite evident that this, instead of being the 

 remains of an organism, is simply the impression made by one of the 

 numerous species of star-fishes (Pala&aster, etc.) which have been found in 

 this group. The lines are probably caused by the arrangement of the 

 plates on the under side of the body ; but the surface of the mud not tak- 



