298 NEW YORK STATE MUSEUM 



but little increased, diverging at an angle that varies between 240 and 300 ; 

 the axil, as a rule, about 90 , while the distal parts of the branches may 

 become horizontal. Sicula small (about 1.2 mm), with short nema and a 

 thin, straight virgella (.6 mm long). Primary thecae bearing longer lateral 

 spines and first eight or more thecae of each branch short, blunt, mesial 

 mucros. Thecae numbering 9 to 1 1 in 10 mm; about 1.5 mm long in the 

 mature parts, overlapping one half their length when mature, and less in the 

 initial part ; the free outer margin straight and subparallel to the axis of 

 the branch. Aperture introverted, opening into a semicylindric excavation 

 which occupies half the width of the branch and one third the length of 

 the free ventral wall of the theca,«leaving an open obliquely recurving notch 

 in the ventral wall. 



Position and localities. The original locality of this species is the Xor- 

 manskill at Kenwood and its horizon the Normanskill shale. It occurs not 

 infrequently in the same horizon at Glenmont and Stockport, but does not 

 seem to be of very common occurrence in any of the localities of the slate 

 belt. It is known to the Canadian geologists from the equivalent shales in 

 Quebec and Gurley has recorded it from homotaxial beds in Arkansas. It, 

 therefore, seems to have had in this country a restricted range. In Great 

 Britain it is also confined to the Glenkiln beds and has been found in South 

 Scotland and Wales and perhaps in Shropshire. In Australia specimens 

 from Stockyard Creek in New South Wales have been, with some doubt, 

 referred to this species. 



Remarks. Hall added the figures of two specimens [see text rig. 212], 

 to the original description, which widely differ in their angles of divergence, 

 stating that the angle varies between 90 and 120" (240' ami 270"). Some 

 of the following observers have regarded those two as representing different 

 species and there exists still at present disagreement as to whether they are 

 conspecific. The monographers of the British graptolites, for instance, 

 concur with Lapworth's former identification in citing the second form alone 

 as representing I), divaricatus, while, on the other hand, Gurley's 

 manuscript contains the following note on this species: 



