68 SILURIAN TRILOBITES. 



time, and, having found a resting-place in the verdict of Prof. M'Coy and myself, must be 

 again disturbed ; for there seems little doubt that, whatever Dalman's C. clavifrons may be, 

 it is not a species with a narrow front to the glabella. Prof. Angelin's figures, quoted under 

 the next species, give us a clue through the uncertainty which has hung over this species ; 

 but unfortunately his scanty description does not enable us to clear it up. Prof. Sars 

 and Dr. Boeck described first one and then a different Trilobite under this name ; and 

 neither was the true species of Dalman, who, as if to justify all the confusion that has 

 since resulted, placed two distinct species together in the Stockholm Museum under the 

 name C. clavifrons, one of which has tlie glabella narrow in front and parallel-sided, and 

 could not have suggested the term (Angelin, 'Pal. Suec.,' t. xxxviii, fig. 9) ; to this one 

 Prof. Angelin has, however, applied the name ; the other, with a subclavate glabella and 

 minute eyes (pi. xxxviii, fig. 10, which does deserve the name C. clavifrons, and to which 

 Prof. Angelin attaches that synonym and the note as to Dalman's authority), he by some 

 strange fatality calls a new species, Cyrtomelopus affinis! 



We shall never have done with the confusion of these forms, unless we restrict Dalman's 

 name to the species called C. affinis by Angelin. In that case I believe our next species 

 will have to forego its baptismal privileges. But pending the settlement of this (and the 

 difficulty is increased tenfold in a genus like Cheirurus, full of closely related and very 

 similar forms), I shall revert to my old name, Ch. juvenis, which sufficiently expresses the 

 smooth contour of the head. It is certainly distinct from all the Swedish forms, though 

 resembling all which have figured under the above name ; and the synonyms given above 

 may, I think, be trusted ; all the specimens have been seen by myself. 



C. juvenis is a large trilobite for this section of the genus, and must have measured 

 three inches in length. It has not yet occurred perfect; but the glabella is rather common, 

 both in Wales and Ireland. It is an ovate and very convex mass, equally attenuate at 

 each end, gibbous along the median line, and regularly convex along a line taken from 

 front to back, not projecting near the base, and scarcely overhanging the front. The 

 furrows are three on each side, the basal one strong, and completely circumscribing the 

 oval basal lobe ; the middle and upper ones gently curved, and equally remote from each 

 other and the basal lobe. The front furrows are placed very forward. 



The cheeks are steeply curved down, but not abruptly so ; the neck-furrow strong, the 

 surface scrobiculate, the eye placed behind the middle furrow, and therefore about half 

 way up the cheek. We have not the free cheeks, but they probably showed a narrower 

 margin than in the following species. The glabella is covered equally with granules and 

 tubercles. Head-spines short. 



Tail with very unequal lobes, the outer ones by far the largest, and produced into stout, 

 slightly divergent spines, with a broad subquadrate base, marked by a short, deep, pleural 

 groove. The two inner pairs are rapidly smaller, the last quite minute. But these vary 

 in length and obtuseness. In our figured specimen they are not longer than the broad, 

 long, conical axis of four joints, which intrudes its last joint between the short terminal 



