GRAPTOLITES OF NEW YORK, PART 1 653 



Remarhs. This species, which originally was considered a later mutation 

 of T. friiticosus, has e\ndently been derived from that species, but by 

 the process of acceleration, the geniculation and the widening of the branches 

 take place so closely to their bases and so rapidly, that this form bears a 

 greatly different aspect from the typical T . f r u t i c o s u s . As it also differs 

 in the arrano^ement of the thecae and is restricted to another horizon, it has 

 the morphologic and stratigraphic value of a separate species. The thecae 

 are more closely arranged than in the mature branch of T. fruticosus, 

 but at the same time they do not develop some of the mature features of 

 those of T . fruticosus, as the}^ do not become so strongly inclined, do 

 not overlap so much and do not possess the conspicuous apertural mucros of 

 the progenitor. In general outline they are clearly a fuller development of 

 the variety which I have designated as T. fruticosus tub if or mis. 

 The earliest thecae of the branches agree still with those of the like stage in 

 T . fruticosus. 



The characters of the proximal parts of the rhabdosome, specially the 

 origin of the first thecae, have not been seen with sufficient distinctness to 

 warrant their description. 



Tetragraptus pendens Elles 



Plate 11, figures 17-20 



Tetragraptus pendens Elles. Quar. Jonr. Geol. Soc. Loud. 1898. 54:491, 



fig.13 

 Tetragraptus pendens Ruedemann. N. Y. State Paleontol. An. Eep't. 1902. 



p.566 

 Tetragraptus pendens Elles & Wood. Monogr. Brit. Grapt. Pal. Soc. for 1902. 



p.61, pi. 6, fig. 2a, b 



On slabs derived from the Didymograptus bifidus zone occur frequently 

 specimens of a small Tetragraptus Avhich have been identified with a form 

 described by Miss Elles froiu the Middle Skiddaw slates. From the species 

 cited as being associated with it ( P h y 1 1 o g r a p t u s cf. t y p u s , 

 Didymograptus g i b b e r u 1 u s ) in the English Lake region, we infer 

 that this organism occurs here in l^eds honiotaxial to the English. 



