204 



SILURIAN TRILOBITES. 



BumastusBarriensis,^^/. G. R. New York, p. 102, No. 10, fig. 4; No. 19, fig. 3, 1843. 



— — Id. Pal.NewYork.vol. ii, p.302,pl.lxvi,fig8. I— 15, 18.52. 

 Ill^nus — Id. 18th Rep. State Cabinet (Dec. 1864); possibly also 7/. 



imperator, id. 



— — Salter. Decades Geol. Surv., No. 2, pi. iii (excl. fig. 2), and 



pi. iv (excl.figs. 9— 11), 1849. 



— — Id. Siluria, 2nd ed., p. 123, Fos?. J 6, fig. 2 (not plate), 1859. 

 [NiLEtis GLOMERiNUSjDaZ. Arsberatt., p. 136,1828; Hisinger; Leth. Suec, p. 16, 1837]? 



Jl. [Bu.) magnus, squamoso-striatus, 6-mcialis, obtuse ovafus, valde convexus nec gihbus, 

 capite semicirculato, caudd transversa. Caput ohtusum sub-truncatum, marginibus obtusissimis, 

 sulcis axalibus brevibus valde convergentibus. Oculi longi hand dejlexi, pidvillo longo 

 fulti, sulco laio pro/undo circumdati. Anguli obtusi. Cauda transversa, semicirculata, 

 convexa. 



This far-famed and common Trilobite has many claims to distinction. Of great 

 actual bulk, for it is remarkably convex; and of no mean linear dimensions, being 

 often nearly 6 inches in length by 3j in breadth ; with the remarkable even contour which 

 induced Sir Roderick to maintain its claims to generic distinction ; with a definite geological 

 horizon, the Lower Wenlock, and with a range from New York to Sweden,— the species, 

 which is a peculiarly abundant one, is perhaps as good an Upper Silurian type as can be 

 pointed out. And the beauty of the specimens, the finest known of which are, I believe, 

 figured on our plate, renders //. Barriensis a general favourite. The largest perfect individual 

 extant is in the cabinet of Miss Jukes, of Birmingham; and as it was carefully figured sixteen 

 years ago in the Decades of the Survey, we have been contented to copy that figure, im- 

 proving it from a good cast. This specimen is 4f inches long by 3 inches 4 lines broad 

 at the head. But our fig. \a, from the Museum of Practical Geology, indicates a yet 

 larger size, — it must have been nearly 6 inches in extreme measurement. 



It may as well, however, be here stated, that the name Barriensis, though evidently 

 intended by Sir R. Murchison for the well-known " Barr Trilobite," was applied by him- 

 self, and subsequently by many different authors, to another and a very distinct species. 

 The figures given in the ' Silurian System ' represent a fossil which I had already 

 distinguished by the name //. pomatia, before I received Prof. Hall's last paper on the 

 fossils of the Niagara group from the Western States. It would be wrong in principle to apply 

 the name intended to designate the common Woolhope Limestone species to another fossil, 

 because that one happened to be figured (in mistake) by its author ; and I think I shall 

 have the consent of all palaeontologists to keep Murchison 's well-known name for the 

 " Barr Trilobite," while Prof. Hall has furnished us with a name for the Dudley one, 

 viz., //. insignis {II. pomatia of our Plate). I subjoin comparative figures of the three 

 Upper Silurian species of this section of the genus, that the distinctive characters may be 

 better appreciated. 



From the lllanits insignis, next described, and usually confounded with our fossil, 

 ]l. Barriensis is at once distinguished by the more depressed shape, the head being regularly 



