4 8 4 



NEW YORK STATE MUSEUM 



pact form, due to its small length (mostly but 6-7 mm) and relatively great 

 width (2 mm when obliquely compressed), the close arrangement of its 

 thecae (14 in 10 mm) and the length of the horizontal, rigid spines 

 (1.5-2 mm). From the rigidity and the direction of the spines a reference 

 to Glossograptus whitfieldi would appear reasonable, and the 

 Cincinnati -specimens have indeed been referred to that species by Ulrich 

 in 1880. The Maquoketa specimens, however, exhibit the peculiar, very 

 narrow or very broad aspects — according to the face exhibited — of the 

 rhabdosome and the spatulate appendages of the spines characteristic of 



Lasiograptus [see fig. 465], and show 



thereby that we have before us a late 



dwarfed mutation of L. bimucro- 



n a t u s. The small size, relatively great 



width, rigidity and length of the spines 



and probably also the scarcity of the forms 



are all characters pointing to the same 



phylogerontic condition of this mutation. 



The Cincinnati specimens are less shortened than the others and have 



still more widely arranged thecae (8-9 in 10 mm) ; they would appear to 



represent a somewhat less reduced mutation than the others. 



Position and localities. I have before me material of this mutation 

 from the higher Utica shales at Flat creek near Mohawk village, N. Y. 

 (in association with Climacogr. put ill us); from the Utica shale 

 at Holland Patent (with Climacogr. t y p i c a 1 i s and Leptobolus 

 in sign is); from the true Utica shale at Cincinnati [Ulrich collection] and 

 from the Maquoketa shale ( Diplograptus bed Sardeson) at Granger, Minn. 

 [Sardeson collection]. 



ADDENDA 

 Note on Dawsonia 

 The history of this genus of somewhat doubtful standing and the 

 description of two species from the Deepkill shales have been given in 

 part 1 of the Graptolitcs of New York. 



Fig. 464-65 Lasiograptus bimucronatus 

 mut. t i m i d u s nov. Fig. 464 Specimen from Utica 

 shale at Flat creek, Mohawk, N. Y. Fig. 465 

 Specimens from Granger, Minn, x 5 



