The Quarterly journal of the Geological Society of London . tes the maximum length as |- inch (15 mm.), butseveral specimens that I have seen are fully 1 inch (25-4 mm.) long,though there seem to be individuals of all sizes from ^ inch(6*3 mm.) upwards. The base shows well, even in badly-preserved specimens, andusually three spinous processes are visible ; the middle probablyrepresents the apertural spine of the sicula (virgella of Tornquist), 520 MISS G. L. ELLES ON THE GEAPTOLITE [Aug. 1898, and the other two are long spinous outgrowths from the bases ofthecae 1^ and 1^. These spines usually
The Quarterly journal of the Geological Society of London . tes the maximum length as |- inch (15 mm.), butseveral specimens that I have seen are fully 1 inch (25-4 mm.) long,though there seem to be individuals of all sizes from ^ inch(6*3 mm.) upwards. The base shows well, even in badly-preserved specimens, andusually three spinous processes are visible ; the middle probablyrepresents the apertural spine of the sicula (virgella of Tornquist), 520 MISS G. L. ELLES ON THE GEAPTOLITE [Aug. 1898, and the other two are long spinous outgrowths from the bases ofthecae 1^ and 1^. These spines usually include between them anangle of about 120°, or sometimes rather less ; they may be straightor slightly curved, are usually rigid, and about ^ inch (8*7 mm.)long. The rigidity and wider angle serve to distinguish them fromthe similar outgrowths in Cryptograjptus Hojphinsoni. The thecae number between twenty-four and twenty-eight to theinch(nine to eleven in 10 mm.), Pig. 31.—Cryptograptus antenna-rius from Outerside and Mun- grisedcde, coll. J. E. Marr. [Nat. size.] the virgula is usually prolongedfor about ^ inch (127 mm.)or more beyond the distalextremity of the specimens show peculiarfeatures. In one, there ap-pear to be two basal spineson the left side of the rhab-dosoma, the occurrence beingsuch as to suggest that a spineproceeded from each of thelower angles of the quadratebasal cell. Whether this isusually the case I am unable to say: I have observed it only in two specimens, and it may bedue to a process of exfoliation during preservation. In the other specimen the basal spines are four in number, twoon each side, and in addition to these there are other spines pro-iecting from the side of the rhabdosoma at a point rather more thanhalfway down its length. The spine on the left is clearly seen,and that on the other side is indicated : both are directed obliquelydownwards. Whether this is merely an accidental occurrence I cannot say ; ifit should prove t
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Keywords: ., bookcentury1800, bookdecade1840, bookidquarte, booksubjectgeology
