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SILURIAN TRILOBITES. 



and linear ungrooved pleurae with free curved spinous ends. The tail is short, with a 

 minute axis of four joints, and is quite truncate below ; its two upper pleurae developed 

 into great divergent spines — the rest obsolete, more so even than in Staurocephalus glo- 

 biceps. 



Deiphon Forbesi, Barrande. PI. VII, figs. 1 — 12. 



Deiphon Forbesii, Barrande, in Hairlinger's Berichte, p. 6, 1850. 



— — Salter. Morris' Cata]., 2nd. ed., p. 106, 1854. 



— — Siluria, 2nd ed., pp. 539, 262, 1859 ; and quoted in 



many general works. 



D. uncialis, latus, granulosus. Glabella spharico-quadrata, oculos impendent, latitudine 

 fere genu- aqualis, granulis creberrimis, maguis minoribusque mixtis. Lobus cervicalis 

 angustus. Spina a base glabella orienfes ; in juniore curva>, tcnuiores ; in alate crassce, 

 sinuosce, retroftexa>, hand patenles. Thorax pleuris antrorsum curvis, ad basin contractu, 

 apicibus recurvis ; anficis poslicisque brevioribus ; ultima brevissimd, et sapissime caudam 

 adharenle, nec connald. . Cauda lata, ad basin truncata, axe 4-annulato stellato depresso* 

 pleuris solum duobus, crassis, patentibus, apicibus recurvis. 



I have been diffuse in the diagnosis, for the reason that I suspect more than one species 

 is confounded under the name of this most odd-looking, rare, and precious Trilobite. Not 

 that fragments are uncommon, they are frequent in the Dudley slabs; but perfect 

 specimens are of the rarest occurrence ; and we are fortunate in being able to present 

 naturalists with the complete form. 



The specimens figured in our plate show that the species must have grown fully an 

 inch long ; and as the breadth is greater than the length, it must have measured one and 

 a quarter inch from tip to tip of the curved spines. The glabella forms the greater part 

 of the head, is hemispherical, rather quadrate in age, but truly hemispheric in the junior 

 stages, or rather subspherical, for it forms at least three quarters of a sphere, and in front 

 it is only somewhat less convex beneath than on the dorsal surface. In very old 

 specimens, fig. 6, the large glabella overhangs the eyes, which are placed close to it on 

 the forward edge of the narrow spine -like cheeks. These arch upward more in young- 

 specimens, so as to be like the figure given by Barrande; but are more horizontal at their 

 origin in the adult. Hence they curve outward and backward (most backward in the 

 older state) and are longer than the width of the glabella itself : they are also covered with a 

 more imbricate granulation ; see fig. 9. The eyes are supported by folds of the crust, which 

 occur both on the fixed cheek behind the eye and on the small triangular free cheek, which 

 last projects a little at the facial suture beyond the spine, and is more finely granular 

 than the spine itself. 



The eyes are (according to Barrande) coarsely granular; — they appear to be more finely so 



