58 TEILOBITES OF GIRVAN. 



axis and its independent convexity, as well as in the ornamentation of the surface. 

 In the head-shield the course of the facial sutures is different, the eyes are 

 further from the posterior margin, the axial furrows are nearly straight and 

 parallel, the free cheeks are of a distinct shape, and the surface is punctate. The 

 head-shield also is relatively shorter and broader than in the typical I. bowmani. 



With I. In tux the pygidium agrees in the characters of the axis, but differs in 

 the position of the fulcrum, in the amount of truncation of the lateral angles and 

 their convexity, and in the ornamentation. The longitudinal median groove behind 

 the axis recalls 7. portlocJci. 



The shape and convexity of the pygidium, truncation of the lateral angles, caudal 

 fascia and ornamentation appear to be similar to I. linnarssoni, Holm, 1 but the 

 resemblance may only be superficial. 



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

 Woodwardian [Sedgwick] Museum. 



llori::nii and Localities. — Balclatchie Group (Llandeilo) : Balclatchie; Ardmillan. 



3. Illaenus barriensis (Murchison), pars, 18:30. Plate IX, figs. 1, 2. 



? 1828. Nileus glomerinus, Dalnian, Arsberatt. Zool. Arbet., p. 134. 



1829. "A New Species of Trilobite," Jukes, Ann. Mag. Nat, Hist,, vol. ii, p. 41, figs. 8—10. 



— " Probably Isotelus," J. D. C. Sowerby, ibid., p. 45. 



? 1833. "Trilobite," Silliman, Amer. Journ. Sci., vol. xxiii, i, p. 203. 



? 1837. Nileus glomerinus, Hisinger, Leth. Suec, p. 16. 



1839. Bumastus barriensis, Murcbison (e.p.), Silur. Syst., p. 656, pi. vi bis (non pi. vii bis, fig. 3, 

 nee pi. xiv, fig. 7). 



1840. Nileus? (Bumastus) barriensis, M. Edwards, Crust., vol. iii, p. 295. 



1842. Illaenus (Bumastus) barriensis, Burmeister, Organ. Trilob., p. 120 (Ray Soc. Edit,, 1846, 

 p. 104). 



1843. Bumastus barriensis, Hall, Geol. Rep. New York, p. 102, No. 10, fig. 4 ; No. 19, fig. 3. 

 1846. Illaenus (Bumastus) barriensis, Keyserling, Reise in Petschoraland, p. 289, pi. ii, fig. 17. 

 1849. Illsenus barriensis, Salter (e.p.), Mem. Geol. Surv., dec. ii, pi. iii (excl. fig. 2); pi. iv (excl. 



figs. 9—11). 



1852. Bumastus barriensis. Hall, Pal. New York., vol. ii, p. 302, pi. lxvi, figs. 1 — 15. 



1854. Bumastus lindstromi, Angelin, Pal. Scand., pi. xxiv, figs. 1, 1 a. 



? - Bumastus? glomerinus, Angelin, ibid., p. 63, pi. xxxiii, figs. 17, 17a. 



1857. Illaenus barriensis, Nieszkowski, Mon. Trilob. Ostseeprov., p. 585. 



1859. Illaenus barriensis, Murcbison, Siluria, 2nd edit., p. 123, Foss. 16, fig. 2. 



1863. Bumastus barriensis, Volbortb, Russ. Trilob., p. 40, pi. iv, figs. 10 — 15. 



1865. Illienus barriensis, Kjerulf, Veiviser, pp. 30, 32, figs. 45 a, b. 



1867. Illienus (Bumastus) barriensis, Salter, Mon. Brit. Trilob., p. 203, pi. xxvii, figs. 1 — 5. 



1875. Illaenus barriensis, Baily, Cbar. Brit, Foss., p. 68, pi. xxiii, figs. 4 a, b. 



Holm, ' Rev. Ostbalt. Silur. Trilob.,' pt, 3, 1886, p. 146, pi. x, figs. 10—23, 



