. Annual report. New York State Museum; Science; Science. GRAPTOLITES OF NEW YORK, PART 2 30I Dicellograptus divaricatus Hall var. rigidus Lapworth Dicellograptus divaricatus Lapworth. Cat. West. Scott. Foss. 1876. pi. 4, fig. 86 Dicellograptus moffaten sis var. divaricatus Lapworth. Belfast Nat. Field Club. Rep't & Proc. v. 1, pt 4. 1877. apx. ; pi. 7, fig. 10 Dicellograptus divaricatus var. rigidus Lapworth. Ann. & Mag. Nat. Hist. Ser. 5, v. 5. 1880. ; pi. 5, fig. 20 Dicellograptus rigidus Gurley. Geol. Sur. Ark. An. Rep't. 1890. 3:416 Dicellograptus rigidus Gurley. Jour.
. Annual report. New York State Museum; Science; Science. GRAPTOLITES OF NEW YORK, PART 2 30I Dicellograptus divaricatus Hall var. rigidus Lapworth Dicellograptus divaricatus Lapworth. Cat. West. Scott. Foss. 1876. pi. 4, fig. 86 Dicellograptus moffaten sis var. divaricatus Lapworth. Belfast Nat. Field Club. Rep't & Proc. v. 1, pt 4. 1877. apx. ; pi. 7, fig. 10 Dicellograptus divaricatus var. rigidus Lapworth. Ann. & Mag. Nat. Hist. Ser. 5, v. 5. 1880. ; pi. 5, fig. 20 Dicellograptus rigidus Gurley. Geol. Sur. Ark. An. Rep't. 1890. 3:416 Dicellograptus rigidus Gurley. Jour. Geol. 1896. 4:297 Dicellograptus divaricatus var. rigidus Elles & Wood. Monogr. Brit. Grapt. (Pal. Soc. 1904.) , fig. 88a; pi. 20, fig. 6a-e This remarkable variety has been described by Dr Gurley from Arkansas as follows: This species resembles in angle of divergence and general outlines D. divaricatus Hall, but may be readily distinguished from that species by the great thickness of the branches (about mm or V16 inch) and especially by the uniformity of the thickness throughout the whole length. This form also differs markedly from Professor Hall's species in character of the base, which is much wider, stouter and more rounded. Hydrothecae about 9 in the space of 10 mm (22 to the inch). The Arkansas form agrees closely with the diagnosis given by Pro- fessor Lapworth for his var. rigidus. As he suggests, this form is entirely distinct from D. divaricatus. Horizon and locality. Dicellograptus zone locality no. 32. W^ 1 , . c , 1 A , Fig. 220 Dicellograptus di- e insert here a drawing 01 the best Arkansas varicatus var. rigidus lsp- worth. Rhabdosome from Arkansas. specimen, made under Dr Gurley's supervision. As Natsize in the British variety the sicular part possesses a small peridermal film or " web," extended between the dorsal sides of the branches. This gives to it a thickened appearance. The thecae are not well shown in any of the Pleas
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