GRAPTOLITES OF NEW YORK. PART 2 



*3 



cf. P t e r o g r a p t u s dilaceratus Herrmann. Nyt Mag. f. Naturvidensk. 1X85. 



27: 190, fig. 7 

 Stephanograptus surcularis Walcott. Geol. Soc. Am. Bui. 1N.90. 10:338 

 S t ep h an gr ap tu s surcularis Gurley. Jour. Cecil. [896. 4:296 

 Nemagraptus gracilis var. surcularis Ellcs & Wood. Monogr. Brit. Grapt. 



pt 3. 1903. p. 1 29, pi. 19, fig. 2a-d 



Hall has figured a series of specimens in the above cited publications 

 [see text fig. 196] as growth stages of N. gracilis, but becoming doubtful 

 [1868, p. 179] of their ontogenetic relation to that species, suggested sur- 

 cularis as an appropriate name for them. This species has been recog- 

 nized by Lapworth and listed by Gurley [1896] as a separate species, but 

 in the Monograph of British Graptolitcs reduced to a variety of N . 

 gracilis. It is stated there : " It was regarded by Hall as a young form 

 of N . gracilis, but 

 if so the direction of 

 the stipes must have 

 been modified at a 

 later stacre of growth 

 of the species, for no W x 97 



Fig. 196-97 Nemagraptus gracilis var. surcularis (Hall). Fig. 196 Copies 

 lorrrp f Arm r\rF>c.F>\- \t of Hall's original figures. Fig. 197 Enlargement (x 5) of the proximal portion of a speci- 

 IdlgC 1U11U piCbCIV- men from Stockport, N.Y. (Original in National Museum) 



ing the aspect of var. surcularis has as yet been found on either side 

 of the Atlantic, although small forms of the type of N. gracilis are not 

 uncommon. We can only consider that they are the same form if we 

 imagine that in the later stages of growth one branch underwent torsion. 

 There appears to be a certain amount of evidence for this view, but it is 

 too small to justify the inclusion of the two under one name." 



We have found this type to be quite common in a layer of the Nor- 

 manskill shale at Glenmont. Here it forms extremely intricate masses, 

 which have a certain rigid habitus in common that suggests at once a dif- 

 ferentiation from the more flaccid, drifted masses of N. gracilis, but 

 on closer examination it is found that these patches while in the majority 

 composed of the r-like rhabdosomes of surcularis, also contain flat 

 S-like rhabdosomes which in no other characters differ from the typical 



