AGNOSTUS CAMBRENSIS. 17 



Bead semi-elliptical, convex, smooth, with very narrow margin. Glabella 

 obsolete, except posteriorly, where if- is barely indicated by a faint line. There 

 is a small median tubercle about one third the length of the head from the neck 

 furrow. Basal lobes indistinctly indicated. 



Thorax: axis wide, with a wide central portion and small lateral knobs. 



Tail : semi-elliptical, convex, smooth, surrounded by a, wide (flat ?) margin, 

 which is of equal width throughout. Axis wide, indicated by two short furrows 

 in front, but obsolete posteriorly. A prominent median tubercle near anterior 

 margin. 



Head- and tail-shields 3'5 — 4 mm. long, 3 — 3*5 mm. wide. 



Perfect specimens are not likely to be mistaken for any other form, but the 

 head by itself might possibly be taken for the head of A. alius. The latter, how- 

 ever, is much larger, and it is completely surrounded by a narrow margin. Tn 

 A. barlowi the margin, when preserved, seems to be confined to the posterior 

 portion of the head. 



Belt's figure and description leave no doubt that his species is the same as that 

 described by Tullberg under the name A. cicer. Fortunately, also, in the Belt 

 collection in the British Museum there is a specimen, probably the original of Belt's 

 figure, with the label Agnostus barlowii. 



Agnostus cicer is recorded by Tullberg from the Gonocori/phe aequalis zone and 

 from the Agnostus intermedins zone, both of which belong to the Varadoxides beds. 

 Belt, on the other hand, states that Agnostus barlowii comes from the Tremadoc, 

 and is associated with Asaphus iiwotatus. As the occurrence of the species in the 

 Paradoxides beds is indubitable, it seems probable that this is one of the very few 

 mistakes in Belt's paper on the Lingula Flags. 



Type. — The specimen registered as 58498 in the British Museum (Natural 

 History) is probably the original of Belt's fig. 18. 



Horizon and Locality. — Probably Menevian : Upper Mawddach. 



Section Limbati. 

 (a) Eegii. 

 14. Agnostus cambrensis, Hicks. Plate II, tigs. 8, 9. 



1871. Agnostus cambrensis, Hicks, Quart. Joum. Geol. Sue, vol. xwii. p, 400, pi. \vi, figs. 11, 12. 

 Non 1872. Agnostus cambrensis, Hicks, ibid., vol. xxviii, pi. v. fig. 1. 



Bead somewhat quadrate, with abroad margin, which is separated from the 

 cheeks by a broad furrow. Glabella bilobed ; the anterior lobe is expanded, nearly 

 semicircular in shape, and highly convex ; the posterior lobe is somewhat narrower 



