PELTURA SCARAB^OIDES. 97 



the eyes seem to be as far forward as in a typical Peltura, and in both the pleurae 

 are described as truncate. It might, perhaps, be well to retain the name Cyclo- 

 gnathus for these and similar species ; but the forms referred to Cyclognathus by 

 Brogger seem to be very distinctly different. 



Practically, therefore, I adopt Brogger's definition of the genus Peltura, and 

 include in it the forms which he refers to the " subgenus Oyclognathus." But I 

 doubt whether these are really congeneric with Linnarsson's Cyclognathus mlcro- 

 pygus, and, provisionally, I look upon the latter as the type of a distinct genus. 



The following are the more important characters of Peltura : 



Head short, subreniform, convex, marginate ; exterior angles rounded (or some- 

 times with short spines). Glabella broad, subrectangular, convex, reaching very 

 nearly to the front margin ; glabellar furrows rather weak, or obsolete. Eyes 

 small, set very close to the anterior angles of the glabella, with a short ocular 

 ridge. Facial sutures with the anterior branches short and converging forwards 

 in front of the eyes; the posterior branches long and leading from the eyes back- 

 wards and outwards to the posterior margin, which they cut near the rounded 

 posterior angles. Free cheeks crescentic. Thorax generally of twelve segments ; 

 axis as broad as the pleurae, or broader ; pleurae grooved, obliquely truncate, but 

 produced into short points. Tail small, wide in proportion to its length, margin 

 armed with short spines or entire ; axis short, thick, ending bluntly, and usually 

 not quite reaching the posterior margin. 



Triarthrus, Green, resembles Peltura in some respects. The genal angles in 

 most of the species are rounded, and the glabella and thoracic axis are both very 

 broad. But it appears to be sufficiently distinguished by the eyes, which are 

 larger and placed considerably farther back and farther from the glabella than in 

 Peltura . 



1. Peltura scarabaeoides (Wahlenberg). Plate XI, figs. 9 — 12. 



1821. Entomostracites scarabieoides, Wahlenberg, Petrif. Tell. Suec, p. 41, pi. i, fig. 2. 



1822. Paradoxides scarabieoides, Brongniart, Crust. Foss., p. 34, pi. iii, fig. 5. 

 1827. Olenus scarabieoides, Dalman, Om Pahead., p. 257. 



1827. Trilobites scarabaeoides, Boeck, Laeren om Trilob., p. 36, pi., fig. 24 (teste Brogger). 



1837. Olenus scarobseoides, Hisinger, Leth. Suec, p. 19, pi. iv, fig. 4. 



1838. Trilobites scarabaeoides, Boeck, Keilhau's Gaea Norv., p. 144. 



1840. Peltoura scaraboides, H. Milne-Edwards, Hist. nat. d. crust., vol. iii, p. 344. 



1847. Peltura scarabieoides, Corda, Prodrom., p. 127, pi. vi, fig. 68. 



1848. Olenus spinulosus ?, Phillips, Mem. G-eol. Surv., vol. ii, pt. i, p. 55, fig. 3, and p. 347. 

 1854. Peltura scarabaeoides, Angelin, Pal. Scand., p. 45, pi. xxv, fig. 8. 



— Anopocare pusillum (pars), Angelin, Pal. Scand., p. 50, pi. xxvii, fig. la (teste Linnarsson). 



A. granulatum, var., can scarcely belong to this genus. Westergard in his Dictyograptusskiffern 

 (Meddel. Lunds Greol. Fiiltklubb, ser. B, no. 4, p. 49) has doubtfully referred them to Bceckia, but 

 figs. 1 and 2 at least seem to belong to Sphaerophthalmus or Ctenopyge, 



14 



