l66 NEW YORK STATE MUSEUM 



Becraft mountain where they were discovered last year by Mr Wardell. 

 They are there associated with a large Desmograptus and quite common, 

 though hitherto not recorded. 



The specimen from Catskill [scr pi. 5, fig. 3] is of especial interest 

 since it shows that the frond had a rather slender infundibuliform shape. 

 It retains both lateral margins for some .distance and also both the upper 

 and lower sides, the two being separated by a shaly layer about 1 mm thick 

 and the lower side exposed at the proximal end of the fragment. 



The thecae could not be seen in any of the specimens. Judging from 

 the length of some fragments the form must have reached quite respectable 

 proportions. One fragment which is clearly but a small portion of the 

 distal part, measures 105 mm in length. Most fragments have as common 

 characteristics the straight, often somewhat rigid direction of the branches 

 and the great thickness and terminal spreading of the dissepiments which 

 give to the fenestrules a circular shape. It is, however, obvious that this 

 species is subject to considerable variation, for on one hand one meets por- 

 tions of the frond where the branches become almost abruptly undulating 

 and a Desmograptuslike structure is approached, as in the distal part of 

 plate 5, figure 3 ; and on the other hand, in large portions both branches 

 and dissepiments become more delicate and the meshes long rectangular. 

 When separated, these so different looking parts of fronds would certainly 

 be taken as belonging to different species, but being parts of continuous 

 fronds, they illustrate the uncertainty of species determination by the 

 character of the meshes in Dictyonema. 



Gurley and Girty published their Devonic Dictyonemas at nearly the 

 same time apparently without knowing of each other's species, for Gurley 

 has not mentioned D. crass u m in his list of 1896, nor in his manuscript, 

 and Girty compares his species only with D. retiforme of the Niagaran. 

 Since the Lower Helderberg formation has now, however, been recognized 

 to be a part of the Devonic, the possibility of the specific identity of this 

 form with the longer known I), hamiltoniae arises, and indeed a 

 comparison of the types of the two forms brings out a strange identity in 



