G80 NEW YORK STATE MUSEUM 



In the Ijase of graptolite bed 3, the lowest outcrop of the zone with D. 

 b i f i d u s, several specimens of an extremely delicate Didymograptus ^Yere 

 collected. These differ in no way from a species first noticed in Sweden. 

 We give here a translation of the original description of the species. 



From an almost uniformly thick sicula of 1 mm in length the two branches 

 diverge at distinctly different hights, the one almost from the middle, the other 

 from the upper end. Above these points of divergence the aperture of the 

 sicula runs obliquely upward, so that, it projects with a triangular tooth 

 beyond the upper branch. The branches are of uniform width, .2 to .3 mm 

 Avide, and diverge almost at right angles from the sicula, but are irregularly 

 bent in their continuation. Within a space of 10 mm 6 to 8 thecae are con- 

 tained. These are long and narrow, with the peiiderm compressed, widening 

 toAvard the aperture to about double the width. The outer Avail of the thecae 

 is slightly concave, sometimes almost straight; it forms a very acute angle 

 with the dorsal margin. The apertural margin is perpendicular on the dorsal 

 margin. Sometimes I believe I have seen a short internal canal. The length 

 of the branches is unknown, but was certainly 15 to 20 mm and probably 

 more. 



Occurs in Phyllograptus shale at Skattungbyn. Fragments of branches 

 are very common upon certain shales. 



To this careful description we need only to add in way of enlargement 

 that the branches are horizontal in their jjroximal part for the length of about 

 three thecae and then mostly become gently reclined, a feature also apparent 

 in Tornquist's dra\vings, or become flaccid ; that the thecae are three to eight 

 times as long as Avide, their slenderness increasing distally, where the greater 

 part of the thecae appears as a A^ery gradually Avidening, hair-fine tube ; and 

 that the angle of inclination of the thecae is not more than 5° in the mature 

 portion of the branches. 



Position and localities. This species is not infrequent in graptolite bed 3 

 (the base of zone Avith D. bifid u s^), Avhere it is associated AA-ith Gonio- 

 g r a p t u s g e o m e t r i c u s and D. nan u s, and it has also been found to 

 occur still rarely in the l^eds at Mt Moreno, Avhich contain a fauna transitional 

 from this zone to that with Diplograptus den tat us. Tornquist 



^ In the Report of the State Paleontologist for 1901, p.556, this form has, as 

 D. (L e p t g r a p t u s ) sp., been erroueously cited from graptolite bed 2. 



