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NEW YORK STATE MUSEUM 



Remarks. This form is, in most respects, a smaller edition of its 

 Hamilton congener D. cadens; and could, with some propriety, be 

 considered as a finer meshed variety of the same. Since, however, at present 

 we have no other criteria of specific determination of a Dictyonema and 

 Desmograptus than the dimensions of their meshwork and transitions 

 between the two Hamilton forms are unknown, the ends of taxonomy seem 

 to be served best by sharply separating them. 



msp 



Fig. 87, 88 Desmograptus vandelooi sp. nov. Enlargements (x 5) of portions of the 

 type specimen showing different aspects of rhabdosome 



Like Desmograptus cadens, this species could be as well 

 referred to Dictyonema as to Desmograptus ; and the final generic deter- 

 mination of the two has to await the finding of complete rhabdosomes. 



cyclograptus Spencer ' 



Spencer's description of this genus is as follows : 



In this genus, the frond consists of a circular disk which was probably 

 cup-shaped in its growing form, though flattened in a concave manner in 

 the rock. From the radicle many stipes radiate through the noncellulifer- 

 ous disk to its margin, and thence in a free manner to some distance beyond. 

 The whole frond resembles a solid wheel, where the radiating spokes extend 

 from the center regularly to beyond the circumference. The branches 

 beyond the disk are celluliferous. The stipes have a central solid axis. 

 The substance is highly corneous, though in some places replaced by pyrites. 



Spencer further points to the resemblance of his genus to the "discoid " 



'Can. Nat. 1882. 10: j 65, jioiii, ■// nudum : Acad. Sci. St Louis, 'trans. 1SS4. 4:503, 

 565, 592; Mus. Slate Mo. Bill. 1884. 1: 13, 15,4-'. 



