GRAPTOLITES OF NEW YORK, PART I 671 



sicula also is either covered entirely or only exposed with its apex, as in 

 figures 17, 18 of plate 13. 



As Hall states that the types of D. constrictus have been associated 

 with D. patulus, it is possible that they may in part at least, represent 

 the constrictiform mode of preservation of that species. The forms, identified 

 by other authors with D. constrictus Hall, may be based on the con- 

 strictifoi-m appearance of still other species. 



Didymograptus nitidus Hall sp. 



Plate 13, figures 1-5; plate 14, figures 5, 6 



Graptolithu8 nitidus Hall. Geol. Sar. Can. Rep't for 1857. p.l29 

 GraptoHthus nitidns Hall. Canadian Organic Remains, decade 2. 1865. p 69, 



pl.1,%1-9 

 Didymograptus nitidus Nicholson (pars), Quar. Jour. Geol. Soc, 1868. 



24:135 

 Non Didymograptus nitidus Nicholson. Ann. and Mag. Nat. Hist, ser.4. 



1870. V.5, p.342, fig.3a-c 

 IDidymograptus nitidus Etheridge jr. Ann. and Mag. Nat. Hist, ser.4. 



1874. 14:6, pl.3, fig.20 

 Didymograptus nitidus Herrmann. Geol Mag. Dec. 3, 1886. 3:15 

 Didymograptus nitidus Barrois. Ann. de la Soc. Geol. du Nord. 1892. 



t.20, p.91 

 Didymograptus nitidus Matthew. Roy. Soc. Can. Proc. and Trans. 1893. 



11:114 

 Didymograptus nitidus Elles (pars). Quar. Jonr. Geol. Soc. 1896. 



64:499-502; p.500, fig.l9; p.501, fig.20 

 Didymograptus nitidus Gurley. Jour. Geol. 1896. 4:295 

 Didymograptus nitidus Elles & Wood. Monogr. Brit. Grapt. pt 1. Pal. 



Soc. vol. for 1901. p.lO, pl.l, lig2a-c 

 Didymograptus nitidus Ruederaann. N. Y. State Paleontol. An. Rep't. 1902. 



p.554, 556 



Description. Primary disk small (diameter about 3 mm), subcircular, 

 tenuously chitinous, with a central node from which the short, thin nema 

 proceeds. Sicula broad and shoit (about 1 . 3 mm hmg), branches diverging 

 in their proximal parts under angles vai'ving between 100" and 180" to a dis- 



