90 TRILOBITES OF GIRVAN. 



Gray's collection. Unfortunately the specimens are not in a completely satisfactory 

 state of preservation, but they indicate definitely a new species which may be 

 known by the name craigeiisis. Probably it was this form which Nicholson and 

 Etheridge referred to as Bronteus, sp. ind. (b) (M., fasc. ii, 1879, p. 166). 



Affinities. — This pygidium bears some resemblance to that of B. hibernicus, 

 Portl., 1 the number of pleurse being the same and the post-axial piece likewise 

 simple, but the shape of the pygidium is different. B. laticauda, Wahl., 2 also 

 appears to be an allied form, but in it the axial furrows are continued posteriorly. 

 II. I a a a I us, Billings, 3 from the Trenton Limestone, bears apparently a closer 

 resemblance. 



Collections. — Mrs. Gray; Museum of Practical Geology ? 



Horizons inn! Localities. — Stinchar Limestone Group (Llandeilo) : Craighead. 

 ? Balclatchie Group (Llandeilo) : Ardmillan (Mus. Pract. Geol.). 



3. Bronteus grayi, sp. nov. Plate XII, fig. 14. 



1879. Bronteus, sp. ind. a, Nicholson and Etheridge, Mou. Silur. Foss. Girvau, fasc. ii, p. 165, 

 pi. xii, fig. 6. 



Specific < 'lin meters. — Pygidium parabolic, very slightly convex. Axis cylin- 

 drical, convex, broad and short, being about one third the width of the pygidium 

 and extending for about half its length ; extremity rounded. Two well-marked 

 broad rings on anterior end of axis, the second ring defined behind by a furrow, 

 which is apparently obsolete in the middle. Axial furrows strong in front but 

 weak posteriorly and faintly encircling extremity of axis. Lateral lobes composed 

 of seven pairs of flattened pleurae; the first six well defined and separated by 

 strong interpleural furrows ; the seventh pair fused in middle line behind axis, the 

 interpleural furrow extending for only a short distance behind it. Sixth pair of 

 interpleural furrows directly continuous with axial furrows, slightly divergent 

 towards posterior margin. All the interpleural furrows die out some distance 

 from the margin of the pygidium. 



First pleura imperfectly preserved. Second pleura of nearly uniform and 

 constant width, bending back rather suddenly at about half its length. Third 

 pleura very narrow at base, but expanding steadily towards extremity. Fourth 

 pleura of-greater and uniform width, curving regularly backward, starting at an 

 angle of about 30° to axial line. Fifth pleura of same width at base as fourth, 

 but expanding towards extremity. Sixth pleura of about same dimensions as the 



1 Portlock, ' G-eol. Rep. Loudoud.,' p. 270, pi. v, figs. 8a, 8fc. 



2 Wahleuberg, ' Nov. Act. Soc. Upsala,' vol. viii, p. 28, pi. ii, fig. 8 (mom. tig. 7). 

 :( Euedemarm, ' Bull. N.Y. State Mus.,' No. 49 (1901), p. 65. 



