GRAPTOLITES OF NEW YORK, PART 2 287 



Nemagraptus gracilis var. approximates nov. 



Plate 16, figures 5, 6 



We have above distinguished a variety of N. gracilis as var. 

 distans which goes beyond the extreme of looseness in arrangement of 

 thecae and reduction of number of secondary branches, properly considered 

 as diagnostic of N . gracilis. 



The present form is a perfect pendant to that variety ; it varies in the 

 same characters but in opposite direction and represents a tendency to 

 closer arrangement of thecae and production of more lateral branches than 

 the typical gracilis possesses. While the latter has but 7 to 9 thecae in 

 10 mm, this has 10 to 12 in the same space of the secondary branches, and 

 the latter are but 1 mm apart (10 stolonal thecae in 10 mm, against 6 to 7 

 in typical gracilis). The overlap of the brachial thecae is correspond- 

 ingly greater and reaches one half the length of the thecae, while the outer 

 margin is slightly more convex and the apertural part also more distinctly 

 introverted [see pi. 16, fig. 6 and text fig. 200, 201]. 



The close arrangement of the thecae of the secondary branches and 

 the small intervals between the bases of the latter will serve to distinguish 

 this variety from other conspecific forms. 



This variety occurs at Glenmont (in association with Dicellogr. 

 sextans) and at the Normanskill (Kenwood). 



Nemagraptus exilis (Lapworth) 



Plate 17, figures 3-9 



Coenograptus exilis, Lapworth. Ms Rep't of 1890 

 Stephanograptus exilis (Lapworth) Gurley. Jour. Geol. 1896. 4:68 



Lapworth's original description, as published by Gurley \loc. cit?\ with 



slight alterations, is : 



Polypary bilaterally symmetric, consisting of two simple (or compound) 

 monoprionidian branches about 40 mm long ; diverging in opposite direc- 

 tions from the center of a minute radicular bar ; branches bearing thecae of 

 type of those of S. gracilis Hall. Width of branches at origin about 

 0.17 mm, proceeding outward at first horizontally (180°), the deflection 



