282 NEW YORK STATE MUSEUM 



the main stipes are relatively wider than the earlier thecae of the secondary 

 branches and above all possess a thicker periderm than any thecae of the 

 lateral branches. The result of this last mentioned difference is a marked 

 contrast in the preservation of the main stipes and lateral branches in most 

 of our specimens, the former being little compressed and glossy, the latter 

 flattened out completely and very frequently so thinned that the thecal form 

 is obscured. The dorsal wall of the main stipes seems to have possessed 

 an especially thick periderm and thereby functioned as a support for the 

 branches, exactly as in Tetragraptus amii (described in Memoir 7, 

 page 536). 



In well preserved specimens, as that reproduced in plate 16, figure 1, 

 it can be seen that the distal parts of the main stipes possess in their thecae 

 the properties of the secondary branches. A number of thecae beyond the 

 last point of budding of a secondary branch, have, however, the small over- 

 lap and thicker periderm of the stolonal thecae and belong clearly to the 

 latter class, although they have not yet thrown off secondary branches. 

 They undoubtedly will do so in the further growth of the colony. 



In the amount of introversion of the apertural parts, there does not 

 seem to exist any appreciable difference between the stolonal and brachial 

 thecae. 



Nemagraptus gracilis var. surcularis (Hall) 



Plate 17, figures 1, 2 



Graptolithus gracilis (part) Hall. N. Y. State Cab. Nat. Hist. 13th An. Rep't. 



i860, p 56, fig. 1-4 

 Graptolithus gracilis (part) Hall. Can. Org. Rem. Dec. 2. 1865. p.13, fig. 



12-15 

 Coenograptus surcularis Hall. N. Y. State Cab. Nat. Hist. 20th An. Rep't. 



1868. p. 179, fig. 13-16 

 Coenograptus surcularis Hall. N. Y. State Cab. Nat. Hist. 20th An. Rep't. 



Rev. ed. 1870. p. 211, fig. 13-16 

 Coenograptus surcularis Lapworth. Cat. West. Scott. Foss. 1876. pi. 3, fig. 64 

 Coenograptus surcularis Lapworth. Belfast Nat. Field Club. Rep't & Proc. 



1877. p. 143, pi. 7, fig. 1 2 



