PLATE II. 



UPPER SILURIAN. 



Fig. 

 1. Phacops Stokesii, Milne-Edwards. Abberley Hills, Wenlock Shale. (Mus. Pract. Geology.) 



2 — 5. ,, ,, From Dudley. (Mr. Mushen's cabinet.) 2 a. Head, enlarged (3 a is 3 



magnified). 4. Tail. 5. Eye, magnified. 



6. Phacops Stokesii. Locality uncertain. Wenlock Shale of N. or S. Wales. (Mus. Pract. Geology.) 



7 — 10. „ Musheni, Salter. Of various ages; from the Wenlock Shale, Malvern. 9 a. Tail, 



enlarged. (Cabinets of J. Mushen, Esq., and C. Ketley, Esq.) 



11,12. ,, „ Larger specimens, Dudley. (Gray collection, Brit. Mus.) 



13,14. Phacops constrictus, Salter. Wenlock Shale, Malvern. 13 a. Tail, enlarged. (Dr. Grindrod's 



cabinet.) 



1.0. „ ,, (15 a, side view ; 15 b, magnified.) 15 c. Eye of the same species. (Mr. 



Ketley's cabinet.) 



16. ,, „ The same species. Wenlock Limestone ; Dudley. (Brit. Mus.) 



17 — 25. Phacops Downingice, Murchison, var. a, vulgaris. All from Dudley and Walsall. Fig. 17, a 



cluster, in the Brit. Mus. Figs. 18, 25, the specimens figured in the 

 original ' Silurian System,' and now in the cabinet of Mr. W. Mathews, 

 junr., of Edgbaston. Fig. 19, half-coiled specimen (Professor Tennant's 

 coll.). Fig. 20, completely coiled (Decades of Geol. Survey). Fig. 21, 

 young ditto (Mr. Mushen's cabinet). Figs. 22, 23, large specimens 

 (Brit. Mus., Gray coll.). Fig. 24, form with large eyes, Malvern, in 

 Wenlock Shale. (Mr. Ketley's cabinet.) 



2G — 29. „ „ Large-eyed variety, /3, macrops. Fig. 2G is copied from the Survey Decades. 



Fig. 27, large specimen, Malvern, Wenlock Shale. (Mr. Ketley's cabinet.) 

 Fig. 28. Dudley. (Brit. Museum.) Fig. 29, internal cast, from 

 Wenlock Rocks, near Cardiff. (Mus. Pract. Geology.) 



30. ,, ,, var. y, inflatus. Malvern Limestone. (Dr. Grindrod's cabinet.) 



31 — 32. ,, ,, . Probably the same variety. Fig. 31, certainly so (glabella only), from 



Ledbury. Fig. 32, internal cast, same locality. Both are figured in the 

 Decade 7, Geol. Survey, and are in the Mus. Pract. Geology. 



33. ,, „ Interior cast of tail. Eastnor, near Ledbury. (Mus. Pract. Geology.) 



Wenlock Limestone. 



34. „ ,, Dissection of the species. (Decades Geol. Survey.) a. Anterior ring, bearing 



the eyes. b. Underside of head (hypostome), bearing the labrum. 

 c. Glabella and fixed cheeks, d. Magnified eye. e. Lenses and interstitial 

 granules, still more magnified. /. Casts of the cups which support the 

 lenses, g. Thorax-joints, h. Underside of the pleurae of ditto, i. Tail 

 of ditto. All more or less enlarged. 



