Memoirs ... Figures and descriptions illustrative of British organic remains. Decade II [VII and XI. Trilobites, with descriptions by J.W. Salter].

  • Geological Survey of Northern Ireland
Date:
1849-1864
Catalogue details

Licence: Public Domain Mark

Credit: Memoirs ... Figures and descriptions illustrative of British organic remains. Decade II [VII and XI. Trilobites, with descriptions by J.W. Salter]. Source: Wellcome Collection.

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    We have seen the eyes of this species, and they are reticulated as in other species of Phacops. But from their greatly curved shape they are generally broken off, and this has led Professor M‘Coy to the establishment of his genus Chasmops, which had better be expunged, as this group is so closely connected with the ordinary Phacops by means of such species as P. Brongniarti and P. Jukesii. Localities.—In Bala Limestone ; Llansaintffraid Glyn Ceiriog, south of Llangollen; Alt-yr-Anker, Meifod, North Wales [M‘Coy], Welshpool [Sil. Syst.] ; Llanfyllin, Montgomeryshire; Llanbedrog, Carnarvonshire [Survey Coll.] ; Applethwaite Common and Coniston, Westmoreland [M‘Coy]. Caradoc Sandstone; Cheney Longville, Shropshire [Sil. Syst., figured specimen] ; Acton Scott, &c., abundant. Section Odontochiee (Dalmannia), Decade II. Pl. 1. Additional British Species. P. mucronalus, Brongn. sp. Entomostrac. caudatus, Wahl. Nov. Act. Soc. Ups., v. 8, t. 2. f. 2. Asaplius mucr. Brongn., Cr. Foss. t. 3. f. 9. Dalman, Pal., t. 2. f. 3 a b. Phacops, Emmrich (1839), Diss. 24. N. Jahrb. 1845. Burmeister, ed. 1. p. 113., and ed. 2. (1846), p. 95. (excl. syn. Murch. “ Sil. Syst.”) Angelin, Pal. Suecica (1852), t. 8. f. 1. P. triuneialis et supra; glabella convexa, antice parum dilatata, utrinque lobis tribus subcequalibus transversis, sulcis longis satisque profuiidis sese scparatis; cauda late tri- angulari acuto, axi subconvexo limbum planum baud aquante, in 9-12 annulos et appendicem trigonalem diviso, appendice in apicem cauda brevi-mucronatum percurrente; lateribus costis 7 planis, sulcis angustis acutis valde curvatis et cum tot lineis intermediis profundioribus ad apices confusis; margine angusto nec distincto. Portions of the head and perfect caudal shields of this rare species have been found in a stratum over the bed of volcanic ash at Pen-y-Rhiw, west of Bala, where it is to be hoped other collectors may obtain fresh specimens. The head is not complete enough to give the diagnosis. Our Bala specimens, as well as those from Sweden in Sir R. I. Murchison’s cabinet, have but 9 rings and a triangular terminal portion to the axis of the tail, but in a specimen from Haverfordwest part of this terminal portion is annulated, and there are 12 rings. The lateral ribs are much arched at their ends, and strongly duplicate, of double furrows, each pair uniting at their tips in a broad depression. The apex is recurved; the mucro varies in length. Localities Pen-y -Rhiw, west of Bala [Survey Coll.] ; Haverfordwest, Pembrokeshire [Mrs. Day’s cabinet] ; in Llandeilo flags. P. amphora, n. sp. P. cauda magna biunciali elongata, convexissima, fere semicylindrica; sulcis axalibus fere obsoletis ; axi lato nec eminenti, marginem caudce hand attingente, in annulos sexdecim sub- pianos diviso, apice obtuso; lateribus valde curvatis deflexis, costis 14-15 planis, sulcis acutis separantibus,—costa, qudque lined medianu Icevi elevatd (sub cortice impressd margine angusto inflexo, apice obtuso (emarginato ?). Very like in general form to P. truncato-caudatus, Port!, from which it is at once distinguished by its convex form (almost like that of a half cask or barrel), and the axis not at all distinct from the sides—the axal furrow being almost obsolete; this latter character is very unusual in Phacops. Along the middle of each of the flattened side ribs a narrow and but slightly elevated ridge runs the whole length ; on the internal cast this is represented by a depressed line of connected dots. Something similar, but less distinct, occurs in the allied species above quoted. Locality.—Grug Quarry, near Llandeilo [Survey Coll.] ; one fine specimen was presented by Mr. Williams, of that place. In Llandeilo flags. August, 1853. J. W. Salter
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