GRAPTOLITES OF NEW YORK, PART 2 \J\ 



tion of the branches of many (supposed zoothecal and gonothecal) tubes 

 gives them the appearance of twisted ropes, a feature that is especially 

 noticeable in the Kashong creek specimens. One of the specimens from 

 Moscow is so far abraded that only the denticles of the thecae are pre- 

 served as black pits. These number 20-22 in the space of 10 mm. A like 

 close arrangement of the thecae is indicated by one of the specimens from 

 Moscow where they are seen in profile on small portions of the twisted 

 branches [see fig. 76]. The thecae in that specimen appear to have had 

 the shape of birds' nests and been flanked by smaller apertures, while the 

 dissepiments are preserved as broad ribbons. 



Dictyonema blairi Gurley 



Plate 3, figure 2 



Dicty on ema blai r i Gurley. 1896. Jour. Geol. 4:82-83 



Proximal end of polypary unknown. Branches radiating slowly, sub- 

 parallel ; usually scarcely but nearly 0.4 mm thick, 0.5 mm occasionally ad 

 max., and arranged transversely, about 20—25 in 25 mm. Interspaces gen- 

 erally about one and one half times as wide as branches or slightly more. 

 Dissepiments rather slender, about 0.25 mm thick ad max.; sometimes 

 straight, usually more or less oblique. Meshes correspondingly variable in 

 shape, from quadrangular to triangular. The shortest are about 1.25 mm 

 long, and the greatest length in unbroken meshes (i. e. where all the dis- 

 sepiments are entire) is probably near 3 mm. Texture black carbonaceous. 

 Branches rather obscurely striate, dividing at an acute, rather sharp angle. 



Resembles somewhat D. gracile Hall, but the branches are a little 

 more slender and the interspaces a little wider, and especially the number 

 of branches transversely in this species is less (20-25 as against 25-30 in 

 D. gracile). I am indebted to Mr Charles Schuchert for having drawn 

 my attention to this species. 



Horizon and locality. Lower Carboniferous (Choteau limestone), 

 Sedalia, Mo. Collected by and dedicated to Mr R. A. Blair, of Sedalia. 



A manuscript note by Gurley reads : 



To this, in the light of more material, I can now add partly by way of 

 correction, that very rarely a single branch may be seen 0.6 mm wide, 

 usually just below a bifurcation ; also that occasional meshes as short as 

 I mm, and very rarely one as short as 0.5 mm, may be found. 



In all 39 specimens, many being fragments. 



On the occasion of discussing the range of the graptolites [Mem. 7, 



