98 BRITISH CAMBRTAN TRILOBTTES. 



1857. Peltura scarabivoid.es, Kjerulf, Geol. d. siidl. Norw., p. 284. 



1864. Olenus scarabieoides, var. obesus, Salter, Brit. Organ. Rem., dec. xi, p. 5, pi. viii. figs. 1 — 4. 



1865. Peltura scarabieoides, Kjerulf, Veiviser ved geol. excurs., p. 2. 



1866. Olenus scarabieoides, Salter, Mem. Geol. Suiv., vol. iii, p. 301, pi. v, figs. 2 — 5. 

 1871. Conocephalus Malvernius, Phillips, Geol. of Oxford, p. 68, fig. 5. 



— Olenus scarabieoides, Phillips, Geol. of Oxford, p. 68, fig. 6. 

 1880. Peltura scarabieoides, Linnarsson, Geol. Foren. Stock. F(irh., vol. v, p. 134, pi. v, figs. 1 — 5. 

 1882. Peltura scarabieoides, Brogger, Die Silur. Etagen 2 und 3, p. 107, pi. i, figs. 7 — 9 ; var. acutidens, 



p. 108, pi. ii, fig. 9.; form, tyjnca, p. 108, pi. ii, fig. 12. 

 1892. Peltura scarabieoides, Matthew, Trans. Roy. Soc. Canada, vol. ix (1891), Sect, iv, p. 53, pi. xiii, 



figs. 9a, b. 



Head about twice as broad as it is long, with a narrow raised border and 

 rounded genal angles. Glabella straight-sided, narrowing slightly forwards, some- 

 what rounded in front, reaching the anterior raised border ; two pairs of oblique 

 glabellar furrows ; neck-furrow well defined ; neck-segment obscurely divided into 

 three parts by oblique furrows running from the middle of the neck-furrow to the 

 posterior lateral angles of the segment, with indications of a median tubercle. 

 Eyes small, placed far forwards and close to the anterior end of the glabella. 

 Facial suture apparently marginal in front, running outwards from the anterior 

 margin to the eye and thence outwards to the posterior lateral angle. Fixed 

 cheeks, triangular, narrow, at their posterior margin about half the width of the 

 neck-segment. Free cheeks crescentie, with a raised margin which is prolonged 

 into a horn in front of the glabella. 



Thorax of twelve segments. Axis wide, nearly twice the width of the pleura? 

 in front, tapering rapidly behind, where its width is but little more than that of 

 the pleurae ; with a row of median tubercles. Pleurae of the anterior segments 

 very short, longer towards the middle of the body, decreasing again posteriorly; 

 fulcrum placed very near the axis ; all the pleurae bent slightly downwards, and in 

 the posterior segments backwards, at the fulcrum, with a dee]) oblique groove; 

 obliquely truncate, but terminating in short points, which, except in the first two 

 or three segments, are directed backwards. 



Tail small, roughly semicircular in general outline, but provided on the margin 

 with three short points on each side. Axis forming about a third of the total 

 width, ending bluntly a little before the margin, divided into two distinct rings 

 and a terminal portion. Lateral lobes with one well-marked furrow on each side, 

 and probably a second shorter one. 



Dimensions. — Fifteen to 20 mm. appears to be an average length, but much 

 smaller and much larger specimens occur. A glabella in the Belt Collection is 

 about 14 mm. long, indicating a total length of more than 40 mm. 



Owing to the pressure to which they have been subjected our British specimens 

 are usually flattened and do not show the marked convexity which is characteristic 



