. Annual report of the Regents. New York State Museum; Science. REPORT OF THE STATE PALEONTOLOGIST 1901 583 tration of a Cambric species published by G. F. In this form the primary branches are short and evidently com- posed of one theca only, while all the branches of a higher order are longer and distinctly figured as consisting of several thecae. If we compare this species with the lower Siluric species of Clonograptus or with the species of Dichograptus and Logano- graptus, e. g. L. logani, where the primary and secondary branches are equally short, a tendency toward a concentrat
. Annual report of the Regents. New York State Museum; Science. REPORT OF THE STATE PALEONTOLOGIST 1901 583 tration of a Cambric species published by G. F. In this form the primary branches are short and evidently com- posed of one theca only, while all the branches of a higher order are longer and distinctly figured as consisting of several thecae. If we compare this species with the lower Siluric species of Clonograptus or with the species of Dichograptus and Logano- graptus, e. g. L. logani, where the primary and secondary branches are equally short, a tendency toward a concentration of the dichotomous branching in the central part of the colony becomes apparent. The genotype of Dichograptus, D. octobrachiatus, and that of Loganograptus, L. logani, are found associated with Goniograptus in the Deep kill section, and occur in younger specimens, which indicate that these genera also conform to the composition of the internodes of one theca each. The denticulate nature of the branches of the first and follow- ing order in Temnograptus was already known to Hall (G r. m i 1 e s i Hall) and has been recognized in its related genera (Holograptus, etc.). Holm has described a coenograptid (Pterograptus e 1 e g a n s),2with a distinct thecal structure in the two principal stems, and the writer figures (fig. 13) a young specimen of Coeno- graptus gracilis itself, which distinctly shows the thecal c^\ | | / structure of these stems. It becomes therefore probable that all parts of the hydrosome of the Dichograptidae, including fun- Fig-13 Coenograptug gracilis Haii. -. , . -, , . , „ Young shows composition lCle and principal Stems, COnSlSt Of of funicle and principal stems of thecae. Normanskill shale of Mt Moreno. x4 thecae; with the exception of the nema, which carries the sicula, and of the central disk. 3 The growth stages of Goniograptus indicate that the bifur- cations of the branches throughout the hydrosome take place in 1 N. Y. acad. sei.
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