02 BRITISH CAMBRIAN TRILOBITES. 



1. Parabolina spinulosa (Wahlenberg). Plate VI, figs. 8 — ] 1. 



1821. Entomostracites spinulosus, Wahlenberg, Petrif. Tell. Suec, p. 38, pi. 1, fig. 3. 



1822. Paradoxidcs spinulosus, Brongniart, Crust. Foss., p. 32, pi. iv, figs. 2, 3. 

 1827. Oh'iius spinulosus, Dalman, Om Palaead., p. 250, pi. vi, fig. 4. 



1837. Olenus spinulosus, Hisiuger, Leth. Suec, p. 19, pi. iv, fig. 2. 



1838. Trilobitcs (jihbosus, var. (pars), Boeck, Keilhau's Ga^a norv., p. 143 (teste Brogger). 

 1843. Paradoxidcs spinulosus, Burmeister, Orgau. d. Trilob., p. 80. 



1854. Parabolina spinulosa, Angeliu, Pal. Scand., p. 40, pi. xxv, fig. 9. 

 1857. Olenus spinulosus, Kjerulf, Geol. d. siidl. Norw., p. 284 (teste Brogger). 



1801. Olenus (Parabolina) spinulosus, Salter, Mem. Geol. Surv., Brit. Org. Bern., dec. xi, pt. viii, 

 pi. viii, fig. 10. 



1804. Olenus (Parabolina) serratus, Salter, ibid., p. 4, pi. viii, fig. 5. 



1805. Parabolina spinulosa, Kjerulf, Veiviser ved geol. excursiouer i Christiania omegu, p. 2. 



1800. Olenus (Parabolina) serratus, Salter, Geol. of North Wales, Mem. Geol. Surv., vol. iii, p. 301, 



pi. v, figs. 0, 7. 

 1873. Olenus (Parabolina) spinulosus, Salter, Cat. Camb. aud Sil. Foss. Mus. Cambridge, p. 11. 

 1882. Parabolina spinulosa, Brogger, Die Silur. Etagen 2 uud 3, p. 100, pi. i, figs. 12 a — e. 

 1904. Parabolina spinulosa, Perssou, Geol. Foreu. Stockholm Forh., vol. xxvi, pi. ix, fig. 24. 



Head forming approximately a segment of a circle but with the anterior 

 margin nearly straight. Glabella rather less than one third the width of the 

 head, almost rectangular but narrowing slightly towards the front and with the 

 anterior angles rounded, reaching forwards nearly to the margin. Three pairs of 

 oblique glabellar furrows, of which the first is shorter, less oblique and less 

 strongly marked than the others ; occipital furrow well defined especially at the 

 sides, the occipital ring divided by two oblique furrows into a central portion 

 which bears a median tubercle, and two anterior lateral portions. Eyes of 

 moderate size, placed far forwards and very close to the anterior angles of the 

 glabella, with which they are connected by strongly marked ocular ridges. Facial 

 suture running directly backwards from the anterior margin to the eye, and thence 

 outwards and backwards to the posterior margin, which it cuts nearly opposite to 

 the extremity of the first thoracic pleura and some distance within the genal 

 angle. Frontal limb very narrow ; fixed cheeks very narrow in front of the eye, 

 widening rapidly backwards, with a strong neck-furrow ; free cheeks ornamented 

 with branching and anastomosing ridges, which radiate from the eye; the posterior 

 margin not in line with that of the fixed cheeks but turning slightly forwards. 

 Head surrounded by a narrow marginal rim and furrow ; genal angles produced 

 into long, slender, backwardly-directed spines. 



Thorax of twelve segments. Axis forming about one third of the whole width, 

 each segment provided with a median tubercle. Pleurae slightly bent downwards 

 towards their outer extremities, produced into spines, which in the first few 

 segments are rather short, but from the fifth or sixth segment onward are of 

 considerable length ; the spines of the first segment directed somewhat outwards, 



