4 



BSITISH FOSSILS. 



surface, instead of the more or less faint radiations of the British 

 fossil. And A. exsculptus (fig. 8). which is still more like ours, has 

 no posterior spines, and a very short glabella. 



We may notice two distinct varieties, possibly species. 



1. A. princeps, a. ornatus, — glabella fere trilohd antice ohtusd, 



limbo radiato-sculjyto, pi. 1, figs. 4, 5. 



2. A. princeps, /3. rudis, — glabelld bilobd, antice acutiori, 



limbo vix radiato, pi. 1, figs. 1, 2, 3. 



British Localities and Geologiccd Position. — Var. a. Lower and 

 Upper Ltngula Flags, figs. 4, 5, from Carreg Wen, near Borth, 

 Portmadoc. Yar. (3. Lower Lingula Flags, figs. 1, 2, Pen-y-foel, a 

 hill close to the Waterfall, Maentwrog, N. Wales (in great abundance). 

 Upper Lingula Flags, fig. 3, Penmorfa Church, near Tremadoc. 

 The species is also found in the Upper Lingula Flags (Black 

 Shales) of Whiteleaved Oak, Malvern, where it was first collected 

 by the late Mr. Hugh Strickland. Upper Tremadoc Slate, Port- 

 madoc. Lower Llandeilo, St. David's Head, rare. 



If I were disposed to divide the genus, as Corda and McCoy 

 have done, the Agnostus tardus, Beyr., A. glabrcdus, Aug., and 

 A, trinodus, Salter, would form a separate group. I prefer to 

 regard them as forming a sub-genus only, TrinoduSf while the 

 species with transverse lobes to the glabella and caudal axis may 

 stand as Agnostus proper, and Condylopyge, Corda. Lastly, the 

 smooth forms with all but undivided caudal and cephalic shields {A. 

 integer, Beyrich, A. glandiformis, Angelin), &c., would form a 

 fourth division, Phalacroma, Corda, as follows : 



Section 1. Condylopyge, Corda. — Glabella distinct and lobed, the 

 forehead lobe wider than, or as wide as, the pos- 

 terior ones. Ex. A. Rex, Barrande ; A, McGoyii, 

 A. Morea, Salter, &c. 



Section 2. Agnostus, Brongn.— Glabella distinctly lobed, the 

 forehead lobe narrower. Ex. A. pisiformis, Brong., 

 A. princeps, Salt. 



Sections. Trmcxitts, McCoy. — Glabella not lobed. 'Fik. A. tardus, 

 Barr., A. trinodus, Salter, &c. 



Section 4. Phalacroma, Corda ? — Glabella or caudal axis scarcely 

 marked out at all. Ex. A. integer, Beyr. English 

 examples doubtful. 



