HAHN, DICTYONEMA-FAUNA OF NAVY ISLAND, X. B. 



143 



long, .5 mm. wide) with terminal expansion to an adhesive bulb (of .8 mm. in 

 width). Branches 10 to 13 in 10 mm. width, .3-.4 mm. wide, closely arranged, 

 sub-parallel, sometimes slightly flexuose. Sicula of one specimen 7 mm. long, 

 determinable as being a very thin tube about 1 mm. in length, with a minute 

 basal disk .3 mm. in width. Within the first 5 mm. 

 of the length of the dendrome, a very frequent 

 branching, sometimes of monopodial aspect, with 

 a common angle of 50-60° takes place. Branches 

 of the third and fourth order are usual, those of 

 the sixth still observable. The interspaces be- 

 tween the branches vary from .3 mm. to 1 mm. in 

 width. Most of the specimens are dorsally de- 

 pressed and therefore, as commonly found in sandy 

 shales, they do not exhibit the theca?. Only a few 



branches, laterally compressed, show 19 to 21 thecse in 10 mm. of length of the 

 branch, as sharp spinelike prolongations, quite similar to those of Dictyonema 

 flabelliforme (cf. Ruedemann (1), p. 601, fig. 26). Very seldom one or the 

 other of these apertural processes reaches the neighboring branch, joining it 

 like a dissepiment. The periderm seems to be composed of two layers, of 

 which the greenish external one adheres to one side of a split slab, while the 

 black interior layer remains on the other side, distinguished by a wrinkled sur- 

 face. Aside from this no striation is visible. 



Fig. 



1. — Callograptits grabaui 

 sp. nov. (3/1) 



Stratigraphic Position and Mode of Occurrence: The type specimen 

 was sent to the Columbia Collection by Victor Ziegler, who obtained the 

 fossil from Center County, Pa., "2000 feet from the bottom of the lime- 

 stone series which are referred by Collie to the Beekmantown." 17 The 

 animal mass is profusely scattered on the sandy surface of the thin- 

 bedded, impure limestone. 



The close relationship of this species to Callograptus salteri Hall and 

 G. compactus Walcott is proved by the following tables it is contrasted 

 only by the distinction of the thecse. 





C. salteri 



C. compactus 



C. grabaui 



Max. observed size 



17 mm. 

 12 



40 mm. 

 13 



15 mm. 

 10-13 



Number of branches in 

 10 mm. width 



I 



Thickness of branches . . 





.5 mm. 



.3-.4 mm. 



.3-.4 mm. 



Number of thecse in 10 mm. 



14-18 



12-14 



19-21 





I 



Thickness 

 ofbranches. 



2 X thickness of 

 branches. 



Average thickness 

 of branches. 



17 This zone may belong to Ulrich's Stonehenge limestone. 



