170 



NEW YORK STATE MUSEUM 



The first (Gurley's) description of this species is : 



Specimens seem very incomplete. Branches radiating rapidly, bifur- 

 cating mostly near the base (in correspondence with their rapid radiation) 

 rather conspicuously longitudinal striate, 0.5-0.6 mm wide, 25-30 in 25 mm. 

 Dissepiments rather stout, wiry, apt to be curved, transverse or slightly 

 oblique. Meshes subquadrangular or with rounded angles. Thecae 

 present but indistinct. Length of mesh uncertain, perhaps 2-2.5 mm - 



Horizon and locality. Devonian (Hamilton formation), Kashong 

 creek, Cayuga county, N. Y. Several specimens, badly preserved but 

 apparently of this species, occur in the Hamilton at Moscow, N. Y. 



All specimens and the type in American Museum Natural History, 



New York city. 



The specimen from Kashong creek which Gurley considers as the 



type of the species, has never been in the Hall collection as Professor 



Whitfield informs me, but was sent to Professor Whitfield 



by B. H. Wright of Penn Yan for identification. On 



the other hand, one of the two specimens from Moscow, 



N. Y., here cited as apparently belonging to this species, 



bears the locality ticket of the old Hall collection and is 



therefore more probably one of Hall's types. Since all 



three specimens are clearly conspecific, the matter is of 



little importance ; and since the species has not been 



figured or described before, no confusion can be created 



by retaining Hall's name for it, while on the other hand, 



the fact that Hall's name has gotten into the literature 



for this, the more common of the two Hamilton species, 



makes the adoption of a new name undesirable. Thus 



e. g. the specimens from the Hamilton shale of the lake 



shore of Erie county, N. Y. referred by Professor Grabau provisionally to 



this species, belong according to his figures undoubtedly hither. 



By way of completion of the above given description, we may add that 



this form receives its characteristic habitus mainly from the rigid straight- 



ness and close arrangement of its thin branches, that, however, the proximal 



portion is distinctly desmograptoid in one of the specimens. The composi- 



Fig. 76 Dictyonema 

 hamiltoniae Hall. 

 Enlargement (x 5) of por- 

 tion of one of the supposed 

 type specimens from Mos- 

 cow, N. Y. in the Am. 

 Mus. Nat. Hist. Shows 

 character of thecae and 

 dissepiments 



