The Quarterly journal of the Geological Society of London . speci-men, only two stipesare seen, and thesedo not exceed ^inch (12-7 mm.)in length. The disc is square and straight-sided, and measures ^ inch (8*5 mm.) acrosseach diameter. The membrane certainly does appear to envelopethe stipes more or less completely, but I think that this must alsobe the case in young forms of Tttragraptus Headi. The specimen is preserved so as to show the apertures of thethecae facing the observer, and these number twenty-four to the inch(nine to ten in 10 mm.). Taking into consideration the form of thedisc an
The Quarterly journal of the Geological Society of London . speci-men, only two stipesare seen, and thesedo not exceed ^inch (12-7 mm.)in length. The disc is square and straight-sided, and measures ^ inch (8*5 mm.) acrosseach diameter. The membrane certainly does appear to envelopethe stipes more or less completely, but I think that this must alsobe the case in young forms of Tttragraptus Headi. The specimen is preserved so as to show the apertures of thethecae facing the observer, and these number twenty-four to the inch(nine to ten in 10 mm.). Taking into consideration the form of thedisc and the number of thecse to the inch, I am inclined to thinkthat this specimen is a young form of Tttragraptus Headi. Occurrence.—The specimen in Mr. Postlethwaites collectionoccurs on a slab on which there are also present Didymograptuspatulus (Hall) and D. gihherulus, Nich.; it belongs probably to theupper part of the Middle Skiddaw Slates. Localities.—South-western end of Eandal Crag, also records a specimen from Barf, near [Nat. size.] 488 MISS G. L. ELLES ON THE GRAPTOLITE [Aug. 1898, (6) Tetragrapttjs cefcifee (Hall). 1858. GraptolWms erucifer, Hall, Geol. Surv. Canada Rep. 1857, p. Graptolithtis erucifer, Hall, Grapt. of the Quebec Group, Geol. , dec. 2, p. 92 & pi, v, fig. 10. 1868. Tetragrapsus erucifer, Nich. Quart. Journ. Geol. Soc. vol. xxiv, p. 144. A specimen in Mr. Postlethwaites collection is the only oneknown to me, therefore it would seem to be rare in the SkiddawSlates. This one Pig. 12.—Tetragraptus erucifer {). agrees very well withHalls description. The general form islike T. quadribrachi-atus (Hall), but thestipes widen verymuch more rapidlyand are much stouter;and the disc is smallerand more oblong thanit is in TetragraptusHeadi (Hall). The stipes widenrapidly from theirorigin, and at thesame time are turnedover on to their sidesso as to revealtheirthecae, though all de-tails are obsc
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Keywords: ., bookcentury1800, bookdecade1840, bookidquarte, booksubjectgeology
