DENDROID GRAPTOLITES OF HAMILTON, ONTARIO. 



23 



thiit this feature serves, in Hamilton collections, as a rather good mark of 

 the species. They are about 55-60 iu 25 mm. 



Horizon and locoUty. — By far the most common species of the genus in the 

 chert-dolomite series at Hamilton, Ontario. I count 38 specimens, which in- 

 clude only a few (selected from many) in the Hall and New York State collec- 

 tions; also one in the Spencer collection labeled " Dicti/oncma gracilc.'' 



In normal polyparies this species is easily distinguished from D. gracilc. Its 

 most characteristic features are the fibrous root, the heavier polypary, espe- 

 cially the much heavier branches at the base, the much more numerous dissepi- 

 ments, and the fewer branches in 25 mm. of width, and (in Hamilton collections) 

 the often well-preserved thecal elevations. Distal fragments of the two species 

 (which, moreover, are rather more apt to be worn) are not always so easy to 

 separate; but those of the present species are apt to be very extensive and 



Fig. 



-5. DiCTYONEMA CRASSIBASALE, NEW SPECIES. RhABDOSOME PRESERVING THE 



FIBROUS PROXIMAL PORTION AND SHOWING THE THEC^, X 1.5. 



somewhere to yield characteristic marks. Usually, of course, they are to be 

 identified by comparison with more perfect specimens. 



The species to which this is most closely related is certainly D. ftplendens. 

 Of that species I have but one specimen, so that I am unable to determine what 

 range of variation it may present. Of the present one, however, I have nearly 

 forty specimens, and with no one of them could I consider Billing's specimen 

 as cospecific. 



After a careful study I am convinced that this is the species which Spencer 

 describes as D. gracile Hall. I base this opinion on his figures, particularly 

 figure 3, the thecfe in which could, as far as the material before me goes, only 

 belong to this species; and on his statements that it has a " noncelluliferous 

 radicle," and that it is the species most easily obtained. Indeed, this species 

 may be known in Hamilton collections by its very great frequency, it being by 

 far the most common species. 

 82651— Bull. 65—09 3 



