154 BRITISH PALAZOZOIC FOSSILS. (Crustacea. 
CERAURUS CLAVIFRONS (Dal. Sp.) Pl. 1. F. fig. 11, 12; and Pl. 1. G. fig. 9. 
Ref. and Syn.—Calymene clavifrons (Dal.) = Chirurus globosus (Bar.) =Spherexochus 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 (Ueber, bohm, Tril. p. 22) supposes to be the C. clavifrons of 
Dalmann, and also with the head ascribed by Lovén 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 were 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 Spherexochus 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—-Applethwaite Common, Westmoreland; 8. W. of Cefn Grugos, Llanfyllin, 
Montgomeryshire (passage beds) ; Cader Dinmael, Denbighshire; Llwyn y Ci, N. W. of Bala, Merionethshire. 
Explanation of Figures.—P|. 1.¥. 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 6. 
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. 9a. Front 
view of another specimen from schists of Cader Dinmael (spaces enclosed by posterior furrows too small in this 
figure of Mr Salter’s.) 
Crravrus ocro-LoBatus (A/°Coy). Pl. 1. G. fig. 10. 
Ref.—M°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 elliptically 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 ealled Sphwrewochus juvenis (Salter)}, but not alluded to in the text. 
Position and Locality—In the limestone of Rhiwlas, N. of Bala Lake, Merionethshire. 
Explanation of Figures —P\. 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. 
+ Corrected subsequently to S. clavifrons (Dal.) in the list of plates prefixed to the same work. 
