FUCOIDES IN THE COAL FORMATIONS. 315 



haps a primary stem (surculus), which is either linear, elongated, apparently tubular, 

 connecting the frond with some point of attachment, or a short, inflated, oval, bladdery 

 tubercle, resembling an organ of suspension in water. These stipes vary in thickness 

 from one-fourth to one-half of an inch, are very abundant on the limestone, much more 

 so than the fronds, appearing like flat cylindrical pipes, mostly simple, curved in many 

 ways, and generally somewhat inflated at one end. I have copied fig. 7 of plateWf as it 

 is seen on the stone. It seems to represent a branching stipe. But this is probably a 

 deceptive appearance, caused by a casual superposition and compression of three different 

 parts of simple stalks. , 



H- RELATION OF THESE FUCOIDES TO OTHER SPECIES OF THE PALEOZOIC AGES. 



These Fucoidal remains so remarkably resemble some of those figured by Mr. Vanuxem, 

 in his Geological Report of New York, under the general name of Fucoides Cauda-galli, 

 Fucoides velum, &c, that their close relation cannot be denied. Specimens of our species, 

 when the rim has been casually destroyed, are exactly like fig. 2, p. 128, of Vanuxem 's 

 Fucoides Cauda-galli. Indeed, except the border, it would be impossible to point out any 

 character which might serve to specifically distinguish them. 



In a re-examination of these fossil plants, the celebrated palaeontologist, Prof. James 

 Hall,* considers the circular form of the frond of Fucoides Cauda-galli as a result from its 

 development around an ascending spiral axis, the frond expanding more and more in as- 

 cending. In consideration of this peculiar mode of growth, the author has grouped the 

 plants of this kind into a new genus, Spirophyton, in which he enumerates four species ' 

 S. Cauda-galli, S. velum, both old species of Vanuxem, and S. typum and S. crassum, 

 two new species. 



Though the very clear descriptions and good figures given by Prof. Hall seem indeed to 

 indicate, at least for his new species, the growth of a frond around a spiral axis, it is plain 

 also that we cannot suppose for the plant here above described a similar mode of develop- 

 ment. The same can be said, I think, of both the forms represented in Prof. Hall's report, 

 the one p. 80, fig. 2, which the author considers as a distorted portion of a last volution of 

 a spiral of Spirophyton Cauda-galli ; and the other, p. 81, fig. 3, named S. velum. For 

 the first of these fronds has, as it has been remarked, exactly the same general form and 

 appearance as the plant represented fig. 2 of our plate, and the other bears at one of its 

 corners the broken remains of what is rightly called a stem by M. Vanuxem, which 

 indicates a mode of growth similar to that of our Caulerpites marginatum. Therefore, 

 these closely related three forms should be forcibly ejected from the genus Spirophyton, 

 this name being inapplicable to plants whose growth has been as a plain untorted lamina. 



The way of reconciling these discrepancies is, I think, to admit that the fronds of this 



* Seventh Annual Report of the Regents of the University of New York, Appendix D, pp. 76 to 84. 



