NEMAGRAPTUS. 125 



out over a considerable distance along the main stipes. The characters of the 

 thecas are somewhat similar to those of A. divergens. 



Horizon and Localities. — Hartfell Shales (zone of Pleurog. linearis). 



8. Scotland : Rowan tree Clench, Kirkhope Bnrn ; Barskeoch Burn. 



Associates, etc. — Only a few specimens have been found ; one is recorded from 

 the Hartfell Shales which occur in the heart of a fold in a small stream flowing 

 into the Kirkhope Bnrn, another from Barskeoch Burn. They are in the collection 

 of the Geological Survey of Scotland. 



Note. 



An interesting- form of Leptograptid is figured on PI. XVIII, fig. 4. Only 

 one specimen, however, has been found, and its affinities are so doubtful that it is 

 merely figured and not named. 



The main stipes are sigmoidally curved and the branches are given off partly 

 in pairs and partly irregularly. The sicula, as figured, is conspicuous, but it is 

 clearly seen to underlie the stipe, and its position may not be the normal one. The 

 thecie, which number eleven to ten in 10 mm. are of the ordinary Leptograptid 

 type. 



Affinities. — In the curvature of the main stipes this form approaches a Nema- 

 graptns, but the mode of branching is rather of the type of an Amphigraptus. Tt 

 is doubtfully referred to this latter genus. 



Horizon and Locality. — Hartfell Shales (zone of J'/eurofj. linearis). 



8. Scotland : Mount Benger Bnrn ? 



Associates, etc. — This form occurs associated with Viplograptus, sp., and is in 

 Lap-worth's collection. 



NEMAGRAPTUS, Emmons (C(EN0RGAPTUS, Hall). 



1855. Nemagrapsiis, Emmons, American Geology, vol. i, p. 109. 



1866. Stephanognijit/us, Cleinitz, " On Hall's GraptoHtes of the Quebec Group," Neues Jalirb. f. Min., 



p. 124. 

 1868. Helicograjisits, Nicholson, Ann. Mag. Nat. Hist. [4], vol. ii, p. 26. 

 1868. Ccenograptvs, Hall, 20th Ann. Report on State Cabinet, p. 217. 



Polypary bilateral, symmetrical, consisting of two slender uniserial main stipes 

 more or less flexed, which may be directed upward, outward, or downward 

 at varying angles, and which originate from the central part of a well-defined 

 sicula. From each of these two main stipes, symmetrically or sub- 

 symmetrically disposed secondary branches may be given off. 



Tliecsc long and narrow, of the general type of Leptographis, with low inclina- 

 tion and small amount of overlap. 



