GRAPTOLITES OF NEW YORK, PART 2 433 



and to C. scharenbergi in others. With the former it lias the uni- 

 form width of the rhabdosome and the form of the thecae — -especially the 

 square shape of the distal part — in common, but differs in the smaller 

 width and greater length of the rhabdosome, the closer arrangement of the 

 thecae, the presence of two lateral spines, the small development of the 

 virgella and the thin, short projecting- nemacaulus. Probably if observed 

 at all, it has hitherto not been differentiated from C. parvus; but its 

 differential and specific characters are constant in the great number of speci- 

 mens occurring" in certain layers. With C. scharenbergi it has the 

 zigzagged sutural groove and the short horizontal side grooves in common, 

 but differs in the considerably closer arrangement of the thecae. Accord- 

 ing to the form of the thecae it is most nearly related to the latter species 

 with which it has especially the zigzagged median groove, the slight intro- 

 version of the free distal part and the abrupt outward bend of the middle 

 part of the thecae in common. Altogether the great number of small square 

 free distal thecae is a feature by which this species will be easily recognized. 



Climacograptus bicornis Hall 



Plate 28, figures 24-26 



Graptolithus bicornis Hall. Pal. N. Y. 1847. 1:268; pi. 73, fig. 2a-s 

 Diplograptus bicornis Geinitz. Die Graptolithen. 1852. p. 24 

 Dip log rapt us bicornis M'Coy. Ann. & Mag. Nat. Hist. 1862. 9:139 

 Climacograptus bicornis Hall. Can. Org. Rem. Dec. 2. 1865. p. 112; 



pi. A, fig. ia-c 

 Climacograptus bicornis Nicholson. Ann. & Mag. Nat. Hist. 1870. 



6:380 

 Climacograptus bicornis Nicholson. Monogr. Brit. Grapt. 1872. p. 61, 



fig. 2 9a-d 

 Diplograptus (Climacograptus) bicornis M'Coy. Prodr. Pal. 



Victoria. Dec. 1. 1874. p. 12; pi. 1, fig. 8 

 Climacograptus bicornis Lapworth. Cat. West. Scott. Foss. 1876. p. 6; 



pi. 2, fig. 51 

 Climacograptus bicornis Lapworth. Geol. Soc. Quar. Jour. 1878. 



34:250 



