722 NEW YOUK STATE MUSEUM 



Diplograptus laxus sp. nov. 



Plate 16, figures 1-10 



Diplograptus sp. nov. Ruedemann. N. Y. State Paleontol. Au. Eep't. 1902. 

 p.571 



A small species of Diplograptus, presenting some very peculiar characters, 

 occurs frequently in bed 7 (zone with D. dentatus) of the Deep kill 

 section and in beds of the same horizon at Mt Moreno. 



Description. Primary disk not observed. Nema short, attaining a length 

 of 9 mm or more, relatively stout, and expanded into a cucumber-shaped 

 vesicle [pi. 16, fig.3]. Rhabdosorae small (maximal length observed 13.4mm, 

 prevailing length only about 10 mm) and nan-ow, as a rule not wider than 

 1 mm, of nearly uniform width. Sicular end provided with two short, 

 curved lateral and a short median spine (the former, apertural spines of 

 first thecae, the latter, probably median spine of sicula). Thecae number- 

 ing 10 to 12 in 10 mm, curved, the angle of inclination increasing from 10° in 

 the basal to 30° in the apertural portion of the thecae; overlapping but 

 one fourth of their length ; their outer margin concave, first subparallel to 

 the axis of the rhabdosome and then turning rather abruptl}' outward. 

 The apertural margin slightly convex and oblique to the general 

 direction of the thecae, forming a short, blunt apertural denticle in the com- 

 pressed material. 



Position and localities. Frequent on the surface of graptolite bed 7 

 (belonging to the zone with D. dentatus) of the Deep kill section and in 

 similar association at Mt Moreno near Hudson. 



Remarhs. I am not aware of any form from which this species could 

 not be readily distinguished either by its small size or the peculiar shape 

 of its thecae. The similarly minute D . p u t i 1 1 ii s Hall, which occurs in 

 the Upper Champlainic shales, has its thecae much less inclined and becoming 

 in their distal portions subparallel to the rhabdosome instead of increasing 

 in divergence as the thecae of this species do. The same difference 

 exists between this species and the equally old, small European form. 



