6 



BBITISH FOSSILS. 



Caract, Emmr. (1839), Diss. 51, bona. A. tesselatus, ib. 50. T. ornatus, Salter, Quart, 



Geol. Journ. (1847), v. iii. 253. (including all synonyms) ; Mem, Geol. Surv., v. ii. pt. 1. 



pi. 9. f. 1, 2. T. Caractaci and T, gihbifrons, M'Coy, Pal. Foss. Woodw. Mus., pi. 1 E. f. 14. 



T. Goldfussii, Barr. (1853), Syst. Sil. de Boheme, pi. 30. f. 29-40. T. ornatus, ib. f. 41-60. 



— Junior (four body rings). Tetrapsellium pulchrum. Corda, Prodr., f. 18. [mala]. 

 T, ovatus latus, fere rotundus, fronte subangulato, glabella, obovatd genis paullo longiore^ 



gibbd, nec lobatd, fimbria subtiis angulatd insuper plana, interduni lente concavd, poris 



crebris guincuncialiter dispositis aut oblique radiatis, in ordines 4-5 concentricos (ad frontem 



scepissime interruptos) collocatis; alis modicis, spinis longis divergentibus ; cervice spinifero ; 



Cauda thorace brevier e, axi convexo ad apicem lente decurvo, later ibus paullo concavis 



radiatim 5-6 sulcatis, margini abrupto declivi. 



There are three if not four principal varieties of this variable species, the differences 

 mainly consisting in more or fewer rows of pores being continued round the 

 front, and the glabella being sometimes as broad as the cheeks and sometimes 

 narrower. But the differences are by no means enough to separate them as species. 

 Variety 5, indeed, differs so much that if it were not for intermediate specimens, 

 it would be difficult to believe it the same. A trifling alteration is necessary in 

 the arrangement of the varieties from that given in the Quart. Geol. Journ. vol. ii. 

 Var. )8. Caractaci. Murch. 1, c. 



— punctis crebris approximatis, ad frontem in ordines 4 continues dispositis, glabella lata. 

 Localities. — Welshpool ; Dinas Mowddwy and Bala, North Wales, in Bala Kocks. 



Var. e. Portlockii. Salter. — T. Caractaci and T. latus, Portlock, 1. c. pi. 1 B. 

 — fimbrid angustiore, punctis ad frontem subradiatis et in ordines 3 contractis; glabella suh- 

 clavatd genis paullo angustiore, caudd brevi. 



Localities. — Tyrone ; Desertcreat ; passing insensibly into the next variety. 



Var. y. elongatus. Portlock, I.e. f. 7. 

 — fimbrid angustd, punctis ut in prcecedenti; glabella angustd clavata ; caudd longiore, 

 apice nec decurvo. 



The lateral ribs of the tail are very distinct in this variety, the elongation of which is 

 not entirely due to pressure and cleavage; several specimens present the same 

 characters ; the whole axis is narrower, the tail longer, and with a raised margin ; 

 the lateral ribs, 6 or 7, very distinct ; the apex not decurved, but rather elevated. 

 We think it merely the male of it. 



Locality. — With the last, Tyrone. 



Most of the Bala, Llandeilo, and Pembrokeshire specimens have the fringe with only 

 three puncta in front, and the glabella short, broad, and gibbous ; they agree per- 

 fectly with T. concentricv^, and help to establish the passage into the next variety. 

 Llandeilo and Pembrokeshire varieties, with narrow glabella, and the puncta in somewhat 

 sunk short radii in front, but with the upper angles of the fringe not expanded, connect the 

 above varieties with — 



Var. 5.favus. Salter, Mem. Geol. Surv. I.e. pi. 9. f. 3. 

 i — capite transverse, rectangidari, fimbrid angustd aniice punctis paucis radiantibus ; angulis 

 externis quadratis, poris magnis favesis; glabelld elongatd. 



Of this curious variety some have the angles more expanded than others. Where 

 the enlargement of the pores takes place the fringe is also convex, and the appear- 

 ance is just that of honeycomb. 

 Localities. — Narberth, &c. in Pembrokeshire ; also Llandeilo ; Middleton, near Chir- 

 bury, Shropshire, 



Var. a. Goldfussii, Barr. (Sternbergii, Salter, Geol. Journ. 1. c) is the Trinucleus so 

 frequent in the sandstones of Bohemia. It differs little from var. )8, except in having 

 closer pores. Specimens of equal size with ours would scarcely differ at all T. ornatus, 

 Stemb., has the pores more remote, and is much more like the common Bala forms 



