BRACHYMETOPUS. IS 



though in a beautiful state of preservation, are so distorted that their exact shape 

 and relative dimensions cannot be ascertained. The pygidia assume, in fact, such 

 different appearances, according to their lie in the stone, as to suggest at first sight 

 that they are specifically distinct ; but Dr. Hicks, who has examined them, confirms 

 my opinion that they all undoubtedly belong to a single species. 



Affinities. — The present species evidently belongs to the genus Phillipsia, and 

 approximates P/t. truncatida, Phillips,^ sp., but differs distinctly in the shape of the 

 glabella, the number of glabella-f arrows, the number of somites in the pygidium,, 

 and in the presence of a distinct broad elevated convex border round both head 

 and tail. 



Fh. gemmuUfera, Phillips, sp.,^ differs in being broader, and in having a shorter 

 thorax and a smooth glabella, and narrower fixed cheeks. 



It may be observed that the ribs of the pygidium seem more definitely distinct 

 and divided than is usual in PJiillijysia or Griffithsides, thus approaching those 

 of Brachijmetopus. From B. ournUca, de Verneuil,"'' which it simulates in that 

 respect, it differs in its broader and more developed border, and in its rings being- 

 only twelve or thirteen instead of seventeen, while its head is of course totally 

 unlike. 



2. Genus — Brachymetopus, M'Goy, 1847. 



This genus is distinguished from its neighbours by the small size and triangular 

 form of the glabella, Dechenella approaching it most nearly in these respects, but 

 differing as well in the greater size of the glabella and its more defined lobes as 

 in the strong striated margin of the pygidium. Several species have been described 

 by M'Coy, H. Woodward, and others from the Carboniferous beds. The following 

 species carries back the genus to the Devonian; while, as CEhlert * points out, 

 Proetus viicropi/gus, Corda," represents it in the so-called Silurian Etages E and F 

 of Bohemia. 



1 1836, Phillips, ' Geol. Yorks.,' vol. ii, p. 240, pi. xxii, figs. 12, 13 ; and 1888, H. Woodward, 

 ' Mod. Carb. Trilobites,' pt. 1, p. 21, pi. iii, figs. 9—14. 



2 1836, Phillips, ' Geol. Torks.,' vol. ii, p. 240, pi. xxii, fig. 11 ; and 1883, H. Woodward, ' Mon, 

 Carb. Trilob.,' pt. 1, p. 17, pi. iii. figs. 1—8. 



3 1845, de Verneuil, ' Geol. Euss.,' vol. ii, p. 378, pi. xxvii, figs. 16 a, b; and 1884. H. Wood- 

 ward, ' Mon. Carb. Trilob.,' pt. 2, p. 48, pi. viii, figs. 1—8. 



* 1885, (Ehlert, ' Bull. Soc. Etud. Sci. Angers,' Ann. 1885, p. (9), pi. i, figs. 1. 2, cf. with 4. 

 » 1852, Barrande, ' Sjst. Sil. Bohem.,' vol. i, p. 445, pi. xv figs. 37—39. 



