BKITISH FOSSILS. 



5 



lobes of the glabella, we have here ventured to unite them ; — the 

 species agrees in all other essential characters. M. Corda in his 

 Prodromus, 1847, next figured an outline of the entire animal and 

 its hypostome, and Barrande's accurate figures complete the illus- 

 trations of this trilobite, 



British Localities and Geological Range. — Llandeilo Flags to 

 Wenlock Limestone. In Lower Silurian, Chair of Kildare, county 

 of Kildare, Ireland ; and in beds of the same age, Carrickadaggan, 

 county of Wexford. In Wenlock strata, Dudley Castle Hill ; 

 Trindle near Dudley ; Walsall (Survey Coll.) 



Foreign Distribution. — In Bohemia ; Komorau, Hills of Listice, 

 Kolednik, &c., in Etage E, Upper Silurian, and also in one of the 

 " colonies" in the Lower Silurian, Etage D, (Bareande). In Sweden, 

 Furudal, Dalecarlia ; in Lower Silurian (Hisinger). In North 

 America, Springfield, Ohio, Upper Silurian. (De Verneuil and 

 Sir C. Lyell.) 



Explanation of Plate HI. 



Fig. 1. Coiled specimen from Dudley; Mr. John Gray's collection. 

 Fig. 2. The same specimen viewed sideways ; a, the terminal boss of the axis of the 

 tail. 



Fig. 3. The head, dissected ; a, a, the strong basal glabella furrows ; b, the small eye ; 



c, termination of the facial suture in front of the posterior rounded angles ; 



d, the rudimentary cheek spine ; e, e, connecting portions of the free cheeks. 

 Fig. 4. Front view of ditto ; a, is the middle glabella furrow ; b, the anterior one ; 



c, c, the free cheeks ; d, the connecting portion, here separated from the 



glabella along the line of the facial suture ; the dotted lines at b indicate the 



natural position in this view of the fixed cheeks, which are much bent down. 

 Fig. 5. Free cheek, with the supine eye (a) actached ; b, the fold of the crust which 



supports the eye, the ^'palpebra inferior" of some authors ; the surface of the 



cheek granulated equally all over. 

 Fig. 6. Magnified portion of the eye ; a, upper surface, obscure in these specimens, 



but probably facetted ; b, lower suface, the lenses fallen out 

 (Figs. 3 to 6 also from Mr. Gray's collection). 

 Fig. 7. Third or fourth thorax ring ; at a, the fulcrum, and b, the prominence against 



which the fulcnmi of the succeeding segment abuts. 

 Fig. 8. Last thorax segment, the fulcrum near the axis. In this and the preceding 



figure the pleurse are represented as flattened out to show their characters ; 



they would appear much shorter on viewing them from above. 

 Fig. 9. Tail ; at a the prominent tip of the axis is shown. 

 Fig. 10. Part of thorax joint ; a, the axis magnified. 



Fig. 11. Basal lobes of the glabella, magnified to show the fine granulation that covers 

 the whole head ; a, the deep circumscribing furrow. 

 (Figs. 7 to 11 are taken from Mr. Fletcher's specimens, Dudley). 

 Fig. 12. A group from Dudley, Mr. J. Gray's collection. 

 Fig. 13. End view of the tail. 



Fig. 14. Head, from the limestone of Kildare ; it is a little elongated by pressure. Other 



specimens show a rounder form. [Survey collections.] 

 Fig. 15. Tail, more elongated than in the Dudley specimens, also from Kildare. 



