76 SIXTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



7. OBSERVATIONS UPON SOME SPIRAL-GROWING FUCOIDAL 

 REMAINS OF THE PALAEOZOIC KOCKS OF NEW-YORK. 



In the higher groups of the Palseozoic rocks of New- York, and 

 of Ohio ^nd Pennsylvania, there are numerous organic remains 

 which have been referred to " Fucoides ; " a term which is often 

 applied to all forms of marine vegetation, or of bodies which 

 have apparently a vegetable origin, but, preserving no fibrous or 

 woody texture or carbonaceous film, are supposed to be of marine 

 origin, and to have grown like the modern fuci. Since we suppose 

 these remains to have been attached to the bottom of the sea 

 during the accumulations of the sediment, and since their sub- 

 stance is scarcely separable from the stony matrix, it is evident 

 that the presentation of these bodies upon the successively ex- 

 posed layers may not always reveal their entire form and charac- 

 ter. It is true that they may have been broken and drifted about 

 like the land plants ; but their texture has not enabled them to 

 resist the action of the waves, and we usually find but unsatis- 

 factory fragments, and of many of these I believe the original 

 form has not been understood. 



In the present remarks, I intend to refer only to those spreading 

 forms which have been termed, by Dr. Locke in the Ohio Geologi- 

 cal Report, " Curtain fucoids ;^^ and similar forms described by Mr. 

 Yanuxem under the same name, and also as the ^^ Retort Jucoid,"^^ 

 the " Fucoides cauda-galli,^^ etc. 



The Fucoides cauda-galli appears to have been the earliest of 

 these peculiar forms. This species, w^hen approximately entire, 

 presents on the surface of the rock a subcircular or oval form, 

 often more or less distorted, but with a subcentral depression if 

 viewed from the upper side, and a corresponding elevation if seen 

 from the lower side. The disc appears to be made up of fascicles 

 which radiate in curving lines from a common centre, and are 

 frequently not distinctly limited on the outer margin. Although 

 these fascicles seem scarcely connected, it seems probable that 

 the form is given by a continuous disc which is thickened in some 

 parts, and these thicker portions give character to the frond. 



The similarity between this species, Avhich has given the name 

 to a formation, and those which are so abundant in some parts of 

 the Hamilton group, is very obvious. Mr. Vanuxem has already 

 made this comparison, and says : 



