16 BRITISH CAMBRIAN TRILOBITES. 



either head or tail. A. eskriggei is very similar to some of the young forms of 

 A. ii minx described by Barrande. 



Horizon and Locality. — Menevian : Dolgelly. A badly-preserved tail which 

 looks like A. nudus var. scanicus, Tull., has been found in the Stockingford Shales, 

 Stockingford cutting, near Nuneaton, and is now in Prof. Lapworth's collection ; 

 but a somewhat similar tail from the same locality seems to show traces of an axis. 

 In view of their imperfect preservation I hesitate to refer them to this species. 



12. Agnostus eskriggei, Hicks. Plate II, fig. 6. 



1872. Agnostus eskriggei, Hicks, Quart. Journ. G-eol. Soc, vol. xxviii, p. 175, pi. v, fig. 7. 



Head smooth, very convex, forming a large segment of a circle ; no trace of a 

 margin visible. Glabella marked only by two very short axial furrows at its base. 



Thorax : axis rather narrow, with a nodule on each side. 



Tail smooth, very convex, forming a large segment of a circle. There is a 

 central portion separated from the rest by a deep furrow, and this is almost 

 circular in shape. The portion outside the circular furrow is nearly uniform in 

 width throughout. 



Head 1*7 mm. long, 2*1 mm. wide; tail 1*6 mm. long, 2*5 mm. wide. 



This species, of which only one specimen is known, resembles A. nudus 

 (Beyrich), and is possibly only a young form. In A. nudus, however, it is clear 

 that the central portion of the tail corresponds with both the axis and the lateral 

 lobes of an ordinary Agnostus, while in A. eskriggei it seems possible, though not 

 probable, that the central portion may represent the axis, and the surrounding 

 part the lateral lobes. If this should prove to be the case the resemblance to 

 A. nudus must be superficial, and there is no known species with which A. cshiggei 

 can be compared. The general appearance of the species is decidedly different 

 from that of a full-grown A. nudus, but is much closer to that of some of the young 

 forms figured by Barrande. These, however, do not show the short axial furrows 

 at the base of the glabella. 



Type. — Hicks's original is in the Sedgwick Museum, Cambridge. 



Horizon and Locality. — Menevian : Porth-y-rhaw, St. David's. 



13. Agnostus barlowi, Belt. Plate II, fig. 7. 



1868. Agnostus barlowii, Belt, Geol. Mag., vol. v, p. 11, pi. ii, figs. 17, 18. 

 1880. Agnostus deer, Tullberg, Agnostus-arterna, p. 26, pi. ii, fig. 16 a, b. 



This figure, as Tullberg notes, is inverted, and the tail is placed above the head. 



