CHEIRURUS. 73 



species are very like this ; C. clavifrons, Dalm., and C. Sarsii, Angelin, have some relation 

 to it ; bnt the C. conformis, from the Wenlock of Gottland, is apparently a near ally, and 

 but for the swelled terminal lobe and wider cheeks, might have been identified with ours 

 (see his pi. xxi, fig. 3.) 



The species is named from the tail only. It is an inch and three quarters broad, and 

 quite transverse, consisting of both axis and pleurae of four segments, which are less con- 

 nected together than usual, even in this genus ; and the pleurae are less metamorphosed 

 than in any that I know. The axis is very broad, and regularly conical ; broadly truncate, 

 reaching to the end of the tail. There are four side-lobes or pleurae, the first two of 

 which are equal in length, and the others but little shorter. All are directed straight 

 outwards for a third of the length, and then curve gently backward, leaving the whole 

 truncate blunt tip of the axis exposed. 



C. cancrurus ? Head, fig. 16. 



The head, which is here provisionally associated with the species, may belong to quite 

 a different one ; for it is much elongated, the length equal to two thirds the breadth. The 

 glabella, including the very prominent neck-segment, is not far short of being twice as long 

 as broad. The basal lobes complete and spherical-triangular, the upper furrows short and 

 somewhat curved. The forehead-lobe is as long as all the rest, exclusive of the neck-lobe. 

 The surface finely granular. The eye placed far back. The fixed cheeks narrow and 

 scrobiculate. The margin strongly marked, but narrow. Spines ? 



Locality. Caradoc limestone of Chair of Kildare, Ireland (Mus. Pract. Geol. The 

 head in the cabinet of Sir R. Griffith, Dublin). 



Section, — Eccoptochile. See p. 61. 



Ch. (Eccoptochile) Sedgwicki. PI. V, fig. 17. 



CkypHjEUs Sedgwicki, M'Coy. Ann. Nat. Hist., 2d ser., vol. iv, p. 406, 1849. 

 Eccoptochile — Id. Synops. Pal. Foss. Woodw. Mus., p. 155, pi. i, f, 



fig. 14, 1851. 

 Cheikurus? — Salter. Morris's CataL, 2nd ed., p. 107, 1854. 



— — Id. Siluria, 2nd ed., p. 538, 1859. 



Ch. (Bccoptoch.) triuncialis, rectangularis, subplanvs, axe angusto, caudd latissimd. 

 Caput (imperfectum) semicirculare ?, glabella genis angustiore, subclavatd, sidcis decurvis, 

 basalibus fere completis ; oculis anticis, genis latis profunde scriptis. Thorax segmentis 12, 

 10 



