56 



[Assembly 



/^"^'^'^Ti^ 



Fig. 4: a, b. A germ or young graptolite, showing the rootlets below and a short axial 



fibre extending above. This is a broad form, apparently of the doubly serrated 



kind; or diplograpsus, and appears to be developed to the first serratures. 



The figures are respectively of the natural size and enlarged. 

 Fig. 5. A minute specimen of a less symmetrical and apparently less fully developed 



form. 

 Fig. 6. Another individual which is farther developed than either of the preceding : 



the line marks the natural size. 



There are several other varieties of form, which, inferring from the central 



midrib, are of those serrated on the two sides of the stipe, as are all those yet 



discovered with the vesicles attached. 



Fig. 7 is apparently the young of one of the singly serrated forms, from the radical 

 fibre extending along one side and beyond the body, while minute fibres (or 

 rootlets? ) extend downwards. 



All these young forms preserve the axial fibre extended beyond the sub- 

 stance of the stipe, and there are usually two or three slender fibres extended 

 below in the direction of the radix. 



Tlie condition of tliese bodies, and their association with those 

 bearing the sacs, is so constant, that I have inferred their connexion, 

 and that these are in fact the embryonic sacs. 



The collection of specimens is quite numerous; but I am still 

 making additions, with the hope that, at no distant period, we may 

 know something more satisfactory relative to this newly observed 

 and peculiar development. 



The following new species of Graptolites appear to be worthy of 

 notice in this place. 



Graptolithus multifasciatus. 



Body consisting of numerous bifurcating branches, wbich are arranged 

 bilaterally on either side of a short strong central bar. The branches 

 bifurcate irregularly, and the subdivisions on one side amount to twenty- 

 one, and on the other to twenty-two, while the specimen is far from being 

 entire. The branches are serrated on one side : serratures somewhat 

 closely arranged. 

 The specimen shows the lower or non-serrated surface, and several of the 



longer branches are turned sufficiently on one side to show the serrations 



in a tolerable degree of perfection. 



