﻿Vol. 66.] THE 0RD0VIC1AN OF THE GLENSATJL DISTRICT. 



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from Stanbridge. We may also compare B. brevispinus 1 from the 

 Chazy Limestone, but its genal angles are less produced. The 

 genus has not been previously recorded from the British Isles. 



Bathytjrtjs cf. timon, Billings. (PI. XXI, fig. 5.) 



There is one fairly perfect pygidium from the tuff (62), which 

 may be compared with Bathyurus timon, Billings, 2 of the Quebec 

 Group, Port aux Choix (Newfoundland). 



It had a similar shape before distortion, and measures 19 milli- 

 metres in length and 27 mm. in width ; the axis, pleural lobes, 

 number of segments, and ornamentation seem to show no con- 

 spicuous points of difference from the Canadian species. 



The genus Bathyurus has been recorded from Argentina by 

 Prof. E. Kayser, 3 and recently by Mr. E. Blackwelder 4 from the 

 Middle Yangtse region in China, associated with a typical Lower 

 Ordovician fauna; but it has not been previously found in the 

 British Isles. 



Bathyurus aff. nero, Billings. (PI. XXI, figs. 4 a & 4 b.) 



One small imperfect head-shield from the tuff (62) with a glabella 

 6 millimetres long, 4*5 mm. wide, and with the head measuring 

 8 mm. in width across the eyes, is referable to the genus Bathyurus. 



In the shape of the glabella and in the tuberculation it resembles 

 Bathyurus strenuus, Billings, 3 but the eyes are set closer in, and 

 have a marginal band. The position of the eyes against the sides 

 of the glabella more vividly recalls B. perspicator, Billings. We 

 may especially compare the head of B. nero, Billings, 7 which has a 

 tuberculated glabella and occipital ring almost identical with those 

 seen in our specimen, but the fixed cheeks are not known. In 

 B. angelini* Billings, from the Chazy Limestone, the position of the 

 eyes and the shape of the glabella are similar ; but the eyes seem to 

 be larger and are set farther back than in this Glensaul specimen. 

 It may also be compared with B. spiniger ( Hall), particularly with 

 regard to the structure of the palpebral lobes, but they are situated 

 farther back in the American species, and the occipital ring has an 

 axial spine. B. extans (Hall) 10 is also allied, though less closely. 

 Both the latter occur in the Trenton Beds. 



1 Raymond, Ann. Carnegie Mus. vol. iii (1905) no. 2, p. 337 & pi. x, 

 figs. 13-15. 



2 ' Paleozoic Fossils of Canada ' vol. i (1865) p. 261 & fig. 244. 



:J Palaecmtographica, Suppl. iii, pt. 2 (1876) pp. 10-12 & pi. ii, figs. 5-8. 

 4 Bailey Willis (& others), 'Research in China' vol. i (1907) pt. i, p. 271. 



6 ' Palaeozoic Fossils of Canada ' vol. i (1865) p. 204 & fig. 188. 

 ,; Ibid. p. 205 & fig. 191. 



7 Ibid. p. 260 & figs. 243a-2±3b. 



s Raymond, Ann. Carnegie Mus. vol. iii (1905) no. 2, p. 335 & fig. 1. 



;) J. Hall, ' Pala?ont. New York.' vol. i (1847) p. 241 & pi. lxiv, fig. 5 ; and 

 J. M. Clarke, ' Lower Silurian Trilobites of Minnesota ' (vol. iii, pt. 2, Final 

 Rep. Geol. Nat. Hist. Surv. Minn.) 1893-97, p. 723 & fig. 38. 



10 J. M. Clarke, op. supra cit. p. 722, fig. 37 & references. 



