GRAPTOLITES OF NEW YORK, TART 1 663 



perflexilis, Tetragraptus fruticosus, Didy mograptus 

 nitid u s. 



Memarhs. This form agrees in the character of its thecae fully mth 

 T. (bigsbyi) similis aad has therefore been first considered by the 

 writer as a variety of that species. The constancy and importance of its 

 differential characters, and the absence of transitional forms to T. similis 

 are, however, sufficient evidence of the fixation of this type and of its 

 specific value. It differs from T . similis piincipally by the greater 

 length, straight direction, obliquely outward growth and regular tapering of 

 the branches. In its central portion and the basal parts of the secondary 

 branches it does not differ materially from T . s i m i 1 i s . I't, therefore, repre 

 sents undoubtedly a further development of that species in a direction, how- 

 ever, different from that leading to Phyllograptus, 



Tetragraptus taraxacum Ruedemann 



Plate 12. flsrures 17-88 



Tetragraptus taraxacum nom. nud. Ruedemann. N. T. State Paleontol. An. 

 Eep't. 1902. p.5S9, fig.l6 



A small but very characteristic form, which is easily recognized among 

 the multitude of species intermixed on the slabs of the Tetragraptus beds 

 (graptolite bed no. 2). 



Desa'iption. The sicula is middle sized and slender (1.3 to 1.7 mm). 

 The two primary thecae, the first of which buds in about the middle of the 

 sicula, are very long, cylindric (1 to 1.4 mm) and diverge at approximately 

 right angles from the sicula. The four ultimate branches which spring from 

 the same are gently curved upward to such an extent that they rise only a 

 little above the apical end of the sicula. The angle of divergence between 

 each pair of branches apparently amounted to as much as 180". Their aver- 

 age length is 6 mm; greatest width 1.4 mm; greatest length observed 9.7mm. 



The first theca of each branch is still long and tubular and provided with 

 a straight apertural margin as the primary thecae ; the following thecae 

 assume rapidly a very different aspect by widening strongly toward the 



