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NEW YORK STATE MUSEUM 



verse notches [see fig. 376, of specimens from Mosher creek]. Also the wavy 

 median furrow of the lateral face is a feature regularly observed in Climaco- 

 graptus but in Diplograptus only seen in the small group, of which D . 

 teretiusculus is the typical representative. The small fragment, asso- 

 ciated with the type and reproduced in figure 370 shows distinctly that this 

 furrow does not begin until about the fourth pair of thecae, a feature also 

 visible, though less distinctly in the type itself. If this furrow indicates 

 that the double series of alternatingly budding thecae has here separated 

 into two coalescing series of successively budding thecae we have another 

 feature, before observed in Climacograptus. 



It is true, the apertural excavations in C. putillus are not as nar- 

 row and slitlike as in a typical Climacograptus, but it may here be remarked 

 that the early thecae of C . t y p i c a 1 i s, are exactly formed like those of 

 C. putillus and that the apertural excavations in that species do not 

 become narrow until the overlap of the thecae has greatly increased. 



Freeh [1896, p. 628] has pointed out the great similarity of this form to 

 Diplograptus teretiusculus and even suggested that it should be 

 regarded as only a variety of that important Scandinavian and English 

 form. Though indeed this European species seems to differ only by attain- 

 ing a greater length and somewhat greater width of the rhabdosome and 

 has approximately the same number of thecae in 10 mm, it appears at much 

 earlier horizons (zone with Didymograptus geminus and Glossograptus ) 

 and is the earliest Diplograptus in Scandinavia, following directly upon 

 subzoner (with Didymograptus bifidus), and approximately of Chazy 

 age. If our form, which for this reason I should keep separate, turns 

 out to be a direct descendant of that Atlantic and Baltic form, it is a 

 very late and interesting survival in the American basin of that old 

 European stock. 



The mutation from the Normanskill shale at Lansingburg, described 

 here, demonstrates that this species existed, though in a rare ami small muta- 

 tion, before Utica time in the Appalachian basin and spread out into the 

 American epicontinental basin in that age. There is even good ground for 



