GO TRILOBITES OF GIRVAN. 



a small proportion Avill ultimately be allowed to remain in it, for there lias been 

 too much breadth of interpretation and frequent erroneous determination of 

 specimens. Amongst the Grirvan specimens it is doubtful if any are truly referable 

 to the typical I. bowmani, and at any rate the very large majority must be 

 distributed amongst other species. Some specimens from Drummuck, however, 

 are perhaps referable to ./. bowmani. The difficulties of identification are increased 

 by the generally poor state of preservation of the fossils. Nicholson and Etheridge 

 figure some specimens from Balclatchie as I. bowmani (ojp. cit.), but they belong to 

 the new species 1. balclatchiensis. 



Holm 1 has suggested that perhaps J. linnarssoni, Holm, ought to be united 

 with J. bowmani; Lint this seems doubtful. 



('oiled ions. — Mrs. Gray ; Museum of Practical Geology ; Edinburgh Museum. 



Horizon and Locality. — Drummuck Group (U. Bala) : Drummuck. 



4 a. Illaenus bowmani, var. longicapitatus, Reed. 



There is a fine specimen in Mrs. Gray's collection of a head-shield with a few 

 thoracic rings attached, which is referable to this variety, 2 which has been described 

 from the Keisley Limestone by the present author. 



Collection. — Mrs. Gray. 



Horizon and Locality. — Drummuck Group (U. Bala) : Starfish Bed. 



6. Illaenus davisi, Salter, 1849. 



1848. Illaenus cmssicauda, Sliarpe (non Dalman), Quart. Journ. Geol. Sue, vol. iv, p. 1411. 



1849. Illsenus davisii, Salter, Quart. Journ. Geol. Soc, vol. v, p. 15. 

 — ■ Illsenus davisii, Salter, Mem. Geol. Surv., dec. ii, pi. ii. 



1852. Illxnus davisii, M'Coy, Syuops. Palseoz. Foss. Woodw. Mus., p. 171, pi. 1 g, fig. 06. 



1854. Illsenus davisii, Morris, Cat. Brit. Foss., 2nd ed.,p. 110. 



— llheims davisii, Murehison, Siluria, 1st ed., woodcut 29, fig. 2. 



1859. Illsenus davisii, Murehison, ibid., 2nd ed., p. 223, Foss. 44, fig. 2. 



1865. Illsenus davisii, Salter, Mem. Geol. Surv., vol. iii, p. 317, pi. xviii, fig. 9. 



1867. Illsenus davisii, Salter, Mon. Brit. Trilob, p. 194, pi. xxix, figs. 10 — 16. 



1876. Illsenus davisii, Armstrong and Young, Cat. West Scot. Foss, p. 16. 



1877. Illsenus davisii, Woodward, Cat. Brit. Foss. Crust., p. 41. 



1879. Illsenus davisii, Etheridge and Nicholson, Mon. Silur. Foss. Girvan, fasc. ii, p. 159. 



1882. Illxims davisii, Holm, Sveusk. Art. Illaenus (Bih. K. vet. Akad. Handl., vol. vii, No. 3), p. 45. 



1 Holm, ' Eev. Ostbalt. Silur. Trilob.,' pt. 3 (1886), p. 153. 

 Keei, 'Quart. Journ. Geol. Sac.,' vol. Hi (1896), p. 412, pi. xx, fig. 5. 



