■■■MHnnjjMMH^' 



GRAPTOLITES OF NEW YORK, PAUT 1 6(( 



the smaller nuinLer of thecae in a unit of lengtli and the general absence of 

 curvature in the branches of D . p at u 1 u s as distinctive cliaracters. Their 

 specimens of the latter species have a looser arrangement than ours (9 to 10 

 in 10 mm), while the thecae in the drawings [p.l4] do not exliibit the curva- 

 ture and inclination desciibed by Hall as characteristic of that species. 



These facts indicate that there is a 

 considerable number of varieties grouping 

 themselves around and between the typical 

 forms of D. patulus and D. nitidus. 



e nave ODSeiVea a piimaiy aiSk Hallsjj. FratrmentofUistaliroition of branch. 



DeepklU. x5.25 



which in the specimen figured [fig, 9J is 



subcircular, fairly well outlined, has a diameter of about 12 mm and though 

 sho^ving but a trace of cai'bonaceous substance, is distinctly set off from the 

 suiTounding surface by its smoothness and depressed margin. Like the 

 primary disks of other forms, it possesses in the center a small, somewhat 

 more projecting circular portion. The apex of the sicula lies upon the apex 

 of this projection and was hence evidently fastened to the disk either by a 

 very short nema or without the intercalation of one. Since in hundreds of 

 otherwise perfect specimens of D . patulus the sicula shows no trace of 

 a nema, I feel satisfied that this species was closely attached to the primary 

 disk, and not suspended by means of a long nema as D. (g i b b e r u 1 u s) 

 c a d u c e u s . 



Didymograptus similis Hall sp. 



Plate U, flgrui-es 25-i» 



Didymograptus simil i s Hall. Canadian Organic Kemains decade 2. 1865. 



p.78, pl.2, lig.1-5 

 Didymograptus similis Gurley. Jour. Geol. 1896. 4:295 

 Didymograptus similis Ruedemann. N. Y. State Paleontol. An. Rep't. 1902. 



p.566, 567 



Description. Nema and primary disk not observed. Sicula small and 

 inconspicuous, about 1.8 mm long. Branches diverging at 180", maximal 

 length attained unknown (longest fragment observed 45 ram); widening 



