GRAPTOLITES OF NEW YORK, PART 2 



2 95 



walls and horizontal, little introverted apertures,' lying in rounded, shallow 

 excavations, that occupy about one third the width of the branch and one 

 fifth the length of the free part of the thecae. 



1 ) . c o m [> 1 a n a t u s is in Great Britain a characteristic graptolite of 

 a zone of the Upper Hartfell shales, occurring in the Moffat and Girvan 

 areas in Scotland and in Ireland ; and in Scania it likewise characterizes a 

 zone of the Trinucleus beds. It occurs hence in Europe in beds overlying 

 the zone with G 1 o s s o g r. qua d r i m ucronatus or beds correspond- 

 ing to our Utica shale and might be expected in rocks of late Champlainic 

 a^e in North America. 2 



Dicellograptus mensurans sp. nov. 



Plate 18, figure 2 



Description. Rhabdosome extremely slender (initial width .2 mm and 

 maximal width but .3 mm); its branches attaining a length of 50+ mm; 

 a short initial part gently concave, so as to form 

 a flat U-shaped axil (angle of this part 240 ), 

 then abruptly becoming convex and curved so 

 as to describe more than one half of the out- 

 line of an ellipse ; the distal ends reapproaching 

 and the whole suggesting a pair of outside cali- 

 pers but also liable to become irregularly 

 twisted. The sicular extremity is blunt, pro- 

 vided with distinct virgella and two hair-fine lateral spines. Sicula very 

 inconspicuous (1.7 mm long). Thecae numbering 10 in the average in 10 

 mm with variations to 9 and 12 at the antisicular and sicular ends; long 

 (about 3.6 mm) and narrow, overlapping one half their length, ventral walls 

 straight and subparallel to axis of branch. Aperture slightly introverted, 

 excavation round, its depth a little more than one third of transverse width 

 of branch. 



1 The form of the thecae is shown at the right of the sicular end in text figure 209. 



2 Freeh \loc. citi\ cites this species also from the Normanskill shale near Albany, 

 probably in error. 



Fig. 210, 211 Dicellograptus men- 

 surans sp. nov. Sicular end and frag- 

 ment of branch enlarged, x 5 



