652 NEW YORK STATE MUSEUM 



more common fonn, the reflection of the branches takes place at quite a 

 distance from the sicula, or initial part of the rhabdosome, and the prox- 

 imal portion of the branches possesses a convex outer margin. The outline 

 of these rhabdosoraes is such as to suggest a section of a bell. We will 

 therefore designate this variety, which is the one originally observed by Hall, 

 asT. fruticosus campanulatus [pl.lO, fig.7]. 



Very different in habit from this are forms which the writer at first 

 believed to represent a different species [pl.lO, fig.2]. The proximal parts of 

 their branches diverge stronger, are concave toward the outside, and the 

 reflection takes place considerably earlier. The result is an outline suggestive 

 of a trumpet ; and we designate this variety asT. fruticosus tubi- 

 formis. This variety approaches Didymograptus V-fractus 

 Salter so much that it suggests itself as the progenitor of that species. 



The nema or nemacaulus of this species is in large specimens inflated in 



the middle and may have been filled with gas to aid in supporting the stout 



rhabdosome. 



Tetragraptus darkei sp. nov. 



Plate 11, figures 11-16 



Tetragraptus fruticosus tnut. {pars). Ruedemann. N. Y. State Paleontol. 

 An. Rep't 1902. p.566 



Description. Primary disk and nema not observed. Sicula long 

 (2 . 6 mm), conspicuous, slender. Four branches dependent, strongly divergent 

 approximately under right angles, curved outward, ^videning rapidly from a 

 width of . 5 ram at their basis to one of 2 . 6 ram or more. Thecae, in the 

 mature portion of the branches numbering 9 to 10 in 10 mra, relatively broad, 

 two to three tiraes as long as wide, about 3 mm long, inclined at an angle of 

 30°, overlapping for one half to two thirds of their length ; straight, their 

 outer walls and apertural margins straight, the latter normal on the axes of 

 the thecae. 



Position and localities. T . c 1 a r k e i has been found only in graptolite 

 bed 3, associated with Goniograptus geometricus, Gronio- 

 g r a }) t u s t h u r e a u i , D i d y m o g r a p t u s s i m i 1 i s and D i d y m o - 

 g r a p t u s b i f i d u s . 



