BEITISH FOSSILS. 



7 



which are intermediate between var. and e. It has long and curved spines, a character 

 which our British specimens are never perfect enough to show. Hall's T. concentricus 

 shows similar variations in the fringe as ours do, but the tail in his figures is made too blunt. 

 We have it from the Hudson River group, of the usual short subtriangalar form. 



There is no end to the variety of names under which this fossil has passed. It 

 appears, from Hall's account in the " Palaeontology, New York, 235, note," that Nuttainia 

 concentrica is the oldest name, having been published in Eaton's Geological Text 

 Book in 1832, and forming the type of his genus. Green's name, Cryptolithus tesselatuSy 

 though published the same year, was subsequent to it. Sternberg's name, T. ornatus, not 

 being put forth till 1833, must give way, and if we have not yet got at the earliest name, 

 we must be ready to change it again. However, as Hall was the companion of Eaton, 

 and collected the very specimens described, his decision must be considered final ; and the 

 name Trin, concentricus must be applied for the future to this cosmopolite fossil. If we 

 were to go back to Llhwyd's name, certainly the earliest of all, it should be T. fimbriatus ; 

 but that would be contrary to rule, and only create confusion. 



In the Quarterly Geol. Journal, vol. iii., p. 253, I have endeavoured to combine the 

 synonyms of the species ; and I see no reason to alter the nomenclature there proposed. 

 I had not then observed that Beyrich had, a year before, suggested the union of T. ornatus 

 from Bohemia with the British fossil ; but this was from figures only. 



Localities. — North and South Wales ; everywhere in Llandeilo and Bala Eocks ; 

 Horderly and Cheney LongviUe in Caradoc sandstone ; Caradoc shale, banks of the 

 Onny, near Cheney LongviUe (Sedgwick). Lower Silurian Rocks of Tyrone, Wexford, 

 and Eildare, Ireland ; not yet in Scotland. 



Foreign Distribution. — North America and Canada. Bohemia. Not yet found in France 

 or Spain, where its place seems to be taken by T. Pongerardi^ Rouault. Nor is it found in 

 Sweden, where T. seticornis is plentiful. 



3. T. Thersites. — sp. nov. 



T. capite lineas 4 lato, semicirculari^ fronte paullum angulato, glabella genis depressis 

 lungiore angustissima valde elevata et acuticarinatd ; fimbria angustd, plana nisi lined 

 mediand paullo incrassatd, punctis satis crebris nec radiatis in ordines ires concentricos 

 collocatis; cervice brevispinoso ; sulco verticali distincto, sub genis latiori; angulis posticis 



haud expansis, spinis ? 



The second or middle row of pores on the fringe is more distinct than the others, on 

 account of the slight swelling of the fringe along that line ; and at the angles a few 

 pores are intersposed between this row and the cheeks. The remarkably elevated 

 and carinated glabella easily distinguishes this species, which has remained long in 

 our collection, indicated as an undescribed Trinucleus in Professor M'Coy's Mss. 

 Locality/. — Tramore, Waterford ; in Lower Silurian slates. 



Section II. Tretaspis, M'Coy. 

 Ocular tubercle distinct ; eye-line cutting the posterior margin, but the head 

 not separable at the sutures ; glabella lobed. 



4. T. seticornis, Hisinger {Asaphus), Leth. Suec, t. 37. fig. 2. A. ct/llarus, ih., fig. 3. 

 T. seticornis, Loven, Ofvers. Kongl. Vet. Akad. (1845), t. 2. fig. 1. Portl. Geol. Rep., 

 pi. 1 B. fig. 8. T. radiatus, ib., fig. 9. T, Bucklandi, Barr. (1846), Not. Prelim. 31. id. 

 Syst. Sil. de Boheme (1853), pi. 30. t 14-16. Tretaspis setic, M'Coy (1851), Pal. Foss. 

 Woodw. Mus. 147. 



T. eUipticus, corpora piano, capite convexo reticulato ; glabella genis longiore clavatd antice 

 inflatd utrinque 2~3-sulcosd; fimbria undique deflexd, insuper convexd, margine recurvo 

 incrassato, subtus planiore ; poris in ordines 5, 6 collocatis, radiantibus; angulis posticis hngi- 

 spinosis, spinis rectis parallelis ; caudd brevissimd rotundatd, lateribus Icevigatis, margini lato 

 declivi. 



The fringe is always steeply bent down, and follows the declivity of the cheek without 

 any change of direction, except in some specimens a gentle convexity. The pores 



