GRAPTOLITES OF NEW YOUK. I'AKT 1 6«)5 



bed 2 of the Deep kill section, on account of their general similarity in early 

 growth stages, to T.bigsbyi Hall. Subsequent, more detailed investiga- 

 tions, and specially a close comparison of these supposed growth stages with 

 the proximal ends of T.bigsbyi, described by Holm, have demonstrated 

 the error of this reference and the fact that these pygmies among the grapto- 

 lites represent a species of their own, which differs in important characters 

 from the other congeners. 



Description. Primary disk chitinous, subcirculai-, of small proportions 

 [fig.l3, about 1mm in diameter]; nema of varying length [fig.ll] ; sicula 

 relatively long (1.4 mm) and slender (width at aperture but .3 mm), with long 

 apertural spines ; projecting beyond the branches of the first oi'der by one 

 fourth or more of its length; branches of first order monothecal, diverg- 

 ing perpendicularly from the sicula, about . 6 mm long ; each producing by 

 dichotomy two branches of the second order, the latter i-eclined ; subparallel 

 to tlie sicula, very small (maximal length observed but 2.7 mm). Thecae 

 very minute, numbering 18 in 10mm, short, twice as ^vide as long; gradually 

 ascending (initial angle about 30°) ; strongly curving outward in the distal 

 parts (80° to 90°), at the aperture twice as wide as at the base. Outer margin 

 strongly concave ; apertural margin slightly concave, provided with acute 

 apertural denticles, Avhich on the two primary thecae appear to develop into 

 spines. 



Position and localities. Quite common in the graptolite bed 2 (belong- 

 ing to the Tetragraptus zone) ; also rarely observed in graptolite bed 3, on 

 slabs with D i d y m o g r a p t u s b i f i d u s and Goniograptus geome- 

 tric u s and in the beds with Diplograptus dentatus at Mt Moreno, 

 near Hudson N. Y. 



RemarJcs. This species is apparently related to T . (b i g s b y i) s i m i 1 i s, 

 with which it agrees in the general form of rhabdosome and thecae. It can 

 be distinguished from growth stages of that larger type by the smallness of 

 its thecae, slenderness and protrusion of the sicula beyond the primary 

 branches and the acute denticles of the thecae. 



