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V.—On Dicellograpsus, a New Genus of Graptolites

Published online by Cambridge University Press:  01 May 2009

John Hopkinson
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Extract

The Graptolites for which the name Dicellograpsus is here proposed are usually included in the genus Didymograpsus, which is thus made to comprise two groups of species which are not only generically distinct, but belong to entirely different sections of the Graptolite family, the species properly belonging to Didymograpsus (D. Murchisoni for example) having hydrothecæ similar to those of Graptolithus, while the species erroneously included in the genus (D. Forchhammeri and others) have hydrothecæ of the type of Climacograptus. This was first pointed out by Prof. James Hall. In his “Graptolites of the Quebec Group” (p. 57) he removed these species from Didymograpsus, and placed them in his new genus Dicranograptus; the species previously known as Diplograpsus ramosus being considered the type of the genus. To this species, and to another then first described, the genus was afterwards restricted by Mr. Carruthers, the remaining species being again included in Didymograpsus. Though fully agreeing with Mr. Carruthers in thus restricting Dicranograptus, I cannot consider the species removed from it as having any alliance to Didymograpsus.

Type
Original Articles
Information
Geological Magazine , Volume 8 , Issue 79 , January 1871 , pp. 20 - 26
Copyright
Copyright © Cambridge University Press 1871

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References

page 20 note 1 Geological Magazine, Vol. V., p. 129.Google Scholar

page 21 note 1 Ann. and Mag. Nat. Hist., series iv., vol. v., p. 351.Google Scholar

page 21 note 2 Mr. Carruthers has verbally informed me that the above is his opinion.

page 21 note 3 Geological Magazine, vol. V., Pl. v.Google Scholar

page 22 note 1 Ann. and Mag. Nat. Hist., series iv., vol. iv., p. 240; vol. v., p. 338.Google Scholar

page 22 note 2 In Diplograpsus, Cephalograpsus, and Climacograptus, theoretically, the angle of divergence is nil, while the radicular angle is 360°.

page 22 note 3 Geological Magazine, Vol. VII., p. 353.Google Scholar

page 23 note 1 Die Grapt., expL pl. v. fig. 28.

page 24 note 1 Geol. Mag. Vol. V. p. 129.Google Scholar

page 24 note 2 The specimen in the Geological Museum (Draw. vi. Tablet 19), labelled “Didymograpsus sextans, Kilnacreagh,” is a good example of Dicellograpsus Forchhammeri, showing the axillary spine, though indistinctly.

page 24 note 3 Grapt. Quebec Group, pl. ii., fig. 19.

page 26 note 1 Dr. Bigsby, in his “Thesaurus Siluricus,” (p. 82) gives “West of Stiper Stones, Shropshire,” as a locality for this species, but this is most probably an error.