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154 BRITISH PALAEOZOIC FOSSILS. [Crustacea. Ceraurus clavifrons (Dal. Sp.) PI. 1. F. fig. 11, 12; and PI. 1. G. fig. 9. Ref and Syn.—Calymene clavifrons (Dal.) = Chirurus globosus (Bar.) = Spheerexochus juvenis (Salt.) Mem. Geol. Surv. (Pt. 1. t. 7. f. 1, 3.—Corrected to S. clavifrons Dalm. in list of plates in same work.) Sp. Ch.—Cephalic shield semielliptical, width twice the length, lateral angles prolonged into short spines; glabella large, ovate, very gibbous, about one-fifth longer than wide, and half as high as wide, minutely granulose; basal pair of segmental furrows wide and deep, curved backwards nearly to the neck- furrow, but not confluent with it, partially enclosing a subovate space on each side about as wide* as the intervening portion of the glabella; middle and anterior pair of side furrows also curved downwards, and nearly as strong as the basal pair, the anterior pair about half the length of the basal, the middle pair rather more; neck-segment strong; cheeks tumid, triangular, much more closely pitted than the glabella; eyes small, on a line with the middle segmental furrow; eye-line going horizontally from thence to the outer margin. Length of head from five to nine lines. This agrees exactly with the head Beyrich (Ueher, b’ohm. Tril. p. 22) supposes to he the C. clavifrons of Dalmann, and also with the head ascribed by Loven to the same species, with the single exception of their not noticing the more coarse pitting of the cheeks, which however might be easily overlooked—if there tvere any doubt on the point Barrande’s name might be used, as his description under the name Chirurus globosus applies exactly. The discrepancy pointed out by Mr Salter in the Mem. of the Geol. Survey does not really exist; our specimen (figure three) shewing the commencement of the prolonged lateral angles beyond what he imagined to be the tumid rounded margin. The reference of the species to Spheerexochus is negatived by the presence of all the characters which distinguish the head of that genus from Chirurus (Ceraurus), namely, the direction of the eye-line, form of the lateral angles, and size of the two anterior pair of segmental furrows. Position and Locality.—Appletliwaite Common, Westmoreland; S. W. of Cefn Grugos, Llanfyllin, Montgomeryshire (passage beds) ; Cader Dinmael, Denbighshire; Llwyn y Ci, N. W. of Bala, Merionethshire. Explanation of Figures.—PI. l.F. fig. 11. Small specimen of glabella, shewing the extent of the seg mental furrows, from the limestone of Llwyn y Ci.—Fig. 11 a. Profile of ditto, magnified.—Fig. 11 A Granulation of ditto, magnified.—Fig. 12. Glabella and part of cheeks of large crushed specimen from Apple- thwaite Common.—PI. 1. G. fig. 9. Profile of part of head, natural size, from Cefn Grugos.—Fig. 9 a. Front view of another specimen from schists of Cader Dinmael (spaces enclosed by posterior furrows too small in this figure of Mr Salter’s.) Ceraurus octo-lobatus (M c Coy). PI. 1. G. fig. 10. Ref.—M c Coy, Ann. Nat. Hist. 2nd Series, Vol. IV. Sp. Ch.—Pygidium transversely elliptical, twice as wide as long, two first rings of the axis narrow, distinct, third or terminal one large, terminating in four flattened ellipticallv pointed lobes; two rather larger similar lobes on each side. Length two and half lines. This curious little species differs from all of this and the allied genera in having the terminal segment of the pygidium quadrilobate, so that the margin of the pygidium exhibits eight marginal pointed lobes in all. It is figured in the Memoirs of the Geol. Survey, from Shole’s Hook, under the same reference as the cephalic shields there called Spheerexochus juvenis (Salter)f, but not alluded to in the text. Position and Locality.—In the limestone of Rhiwlas, N. of Bala Lake, Merionethshire. Explanation of Figures.—PI. 1. G. fig. 10. Pygidium, natural size from Rhiwlas.—Fig. 10 a. Ditto, magnified. * Mr Salter’s figure in this work, and those of this species in the Mem. of the Geol. Survey, are deceptive in this particular. f Corrected subsequently to S. clavifrons (Dal.) in the list of plates prefixed to the same work.