EXPLANATION OF THE PLATES. 81 
PLATE XXVII. 
FOSSILS OF THE LUDLOW ROCKS. 
CRUSTACEA.— TRILOBITA. 
Fic. 1.—Homatonotus Knicuru, Konig. 
Tcon. Foss., fiig. 65. H. Knightii and Ludensis, Sil. Syst., pl. vii., figs. 1-4. 
H. Knightii, Siluria, 4th ed., pl xix., figs. 7-9. 
From the figure in Sil. Syst., pl. xix., fig. 8; side view. Upper Ludlow, Ludlow. 
Luriow.—Sil., 4th ed., p. 518. ‘* Very characteristic of the Upper Ludlow 
rock ;” ibid., p.235. Localities: Shropshire, Herefordshire, Worcester- 
shire, Radnorshire, Brecknockshire. Sil. Syst., p. 651. Kendal, Pem- 
brokeshire, Freshwater, East, and Henllyn Hill, Builth. Mus. G. S. I. 
- PHYLLOPODA. 
Fig 2,—CERATIOCARIS PAPILIO, Salter. 
From Ann. and Mag. Nat. Hist., 1860, p. 154, fig. 3. 
Ludlow.—Sil., 4th ed., p. 516. “ Upper and Lower Ludlow (black flags), 
Lesmahago, Lanarkshire.” Ann. Nat. Hist., p. 156. 
EURYPTERIDA. 
Fig. 3.—a, 6. PTERYGOTUS PROBLEMATICUS, Agassiz. 
Sil. Syst., p. 606. Poiss, Vieux Grés Rouge, pl. i. 
a. Portion of the fixed ramus of the antennary chela, from the figure in 
Mem. Geol. Surv., Mon. i., pl. xii., fig. 9. Upper Ludlow rock, Hagley 
Park, Herefordshire. Mr. J. Harley’s collection. 
b. Anterior segment of the body ; reduced one-third, from fig. 20 on the 
same plate (same collection). Locality: Ludlow. 
e. Surface markings (slightly enlarged). 
WENLOcK to LupLow and PassaGeE Bens, or base of Old Red Sandstone.— 
Sil., 4th ed., p. 521. ‘* Characteristic of the Upper Ludlow Rock ;” 
ibid., p. 238. Mr. Salter describes it, in the monograph just quoted, p. 93, 
as ‘“‘one of the most widely spread species.” He mentions several 
localities in Upper Ludlow rock near Ludlow, Kendal, Westmoreland, 
Bone-bed, Ludlow, Downton Sandstone, Kington. Base of Old Red Sand- 
stone, Railway Station, Ludlow, Cornstones of Hopton Gate; and as 
