56 



[Senate 



The second step in the progress of development, which has been observed, is 

 shown in fig. 2, which is from a very beautiful specimen' in the collection of Mr. 

 R. P. Whitfield: in this one, the general form is similar to that of fig. 1, but it is 



Fig. 1. 



Fig. 2. 



somewhat larger, and there are five lateral branches on each side. Another indi- 

 vidual, somewhat farther advanced, presents eight or nine branchlets on either 

 side, as shown in fig. 3. 



Fig. 3. 



Fig. 4. 



%. 5. 



At the same time it is not easy to see at once how this form should assume the 

 S-form so common in the specimens observed, and consequently it is difficult to 

 illustrate every stage of the process. We do observe, however, that the main 

 stipes become more curved as they progress; and it is only necessary to spread out, 

 on a flat surface, these two stipes in opposite directions and rectangularly to the 

 direction of the small branches, and we should have a form approaching that in 

 which these fossils usually occur. 



The small specimen which I had referred to Rastrites in my communication to 

 the Regents' Report, is simply one-half of one of those young individuals of G. 

 gracilis, where the young branches are thickened and not distinctly serrate (fig. 4)*. 



In the original specimen of G, gracilis there is a slight interruption in the con- 

 tinuity of the main stipe, as is observed in many individuals of that form; and 

 there is likewise a small process which may be the radicle, as shown in the accom- 

 panying fig. 5, of a small specimen preserving the usual form of this species : this 

 figure is of the natural size. 



The accompanying fig. 6 (on the opposite page), of a very beautiful specimen of 

 the G. gracilis y is from the same locality as all the others known to me, but shows 

 a greater development of the branches and a more distinct serration than any 

 others in the collection! . 



* The specimen figured in Emmons's American Geology, Plate 1, fig. 6, and described as the 

 type of a new Genus NemagrapttJs, is evidently a fragment of G. gracilis. 



\ Although the main stipe was represented as continuous, it is nevertheless partially cov- 

 ered in the centre, or at the radicle -point by the overlapping of one of the bent branches and 

 a little adhering stone. 



