688 XEW YOKK STATK MUSEUM 



Didymograptus tornquisti sp. nov. 



Plate 13, figures 8, 7 



Desn'iption. Pnmarv disk unknown ; nema present. Siciila small (1 . 2 

 mm). The point of origin of the first theca has not been distinctly observed. 

 The branches diverge near the apertnral end of the sicula, are nearly honzontal, 

 gently curved, attaining their full width (1.1 mm) near the proximal part 

 and maintaining it. Thecae numbering 8 in 10 mm, inclined at an angle of 

 about 20", three times as long as wide, in contact about one third of their 

 length. Outei' and aj)ertural margins straight, the latter normal on direction 

 of axis of theca. 



Position and locality. In graptolite bed 3 (zone of D . b i f i d u s) asso- 

 ciated with Goniograptus geometricus, Tetragraptus pen- 

 dens, D . b i f i d u s and D. similis. 



Remarlii^. Only one specimen of this species has been observed. Its 

 principal characters, viz the loose arrangement and low inclination of the 

 thecae and the small amount of overlap, distinguish it from other forms 

 except D. af finis Nich., which however has much narrower branches 

 and a shorter sicula. From the similar D. nicholsoni var. planus, 

 which occurs in the underlying bed, it differs by the smaller number of 

 thecae in a unit length. 



Didymograptus spinosus sp. nov. 



Plate 14, flgures 30-32 



Description. Primary disk and neraa not observed. Sicula small and 

 little conspicuous (.9 mm). First thecae diverging suborally. Branches 

 moderately deflexed, their angle of divergence about 120°; very thin at the 

 beginning (not .3 mm wide), but widening rather rapidly within 10 mm to 1 

 mm. Mature length and width of branches unknown ; the longest branch 

 observed attains a length of 16 mm. Thecae numbering 12 in 10 mm ; nar- 

 row, four times as long as wide in the proximal and three times as long as 

 ■wide in the more distal parts of the I'habdosome ; inclined at 20*^ ; in contact 



