12 BRITISH CAMBRIAN TRILOBITES. 



surface of the cheeks and lateral lobes of the tail is much more distinct than in 

 Tullberg's figure. 



Synonym;/. — Salter's Agnostus princeps was founded on specimens of three 

 distinct species. His figs. 4 and 5 are from specimens of A. trisectus, fig. 1 

 from A. pisiformis, and fig. 3 from A. rudis. 



In 18G8 Belt [he. cit.) recognised that the differences between A. princeps and 

 A. trisectus were very small, and that it was often practically impossible to dis- 

 tinguish between the two, but he did not actually unite them because Salter was 

 about to treat the genus in his ' Monograph.' Unfortunately, Agnosias is one of 

 the genera which Salter did not live to complete. 



Not infrequently in imperfect specimens the threefold longitudinal division of 

 the last segment of the axis of the tail is barely visible, while the keel on the 

 first two segments is still distinct, and this, perhaps, led Salter to conclude that he 

 had two distinct species to deal with. The specimens which are called A. princeps 

 in collections labelled by Salter are generally -4. trisectus, occasionally A. pisiformis. 



Types. — A sealing-wax cast of the original of Salter's fig. 11 is in the Geological 

 Survey Museum, registered as 8768. The original of his Agnostus princeps, var. 

 omatus, fig. 4, is also in the same museum, registered as 8741. 



Horizon and Localities. — Upper Lingula Flags : Carreg Wen, Borth ; Moel 

 Gron ; near Craig-y-Dinas, Mawddach ; Maentwrog ; Yr Orsedd, Blaenau Ffesti- 

 niog ; Penmorfa; Ogof-ddu, Criccieth ; S.E. of Tryweryn ; Malvern Hills. 



Section L^evigati. 

 8. Agnostus altus, Gron wall. Plate II, fig. 1. 



1902. Agnoshis alius, Gronwall, Bornholms Paradoxideslag, p. 58, pi. i, figs. 3, 4. 



Head rounded, smooth, uniformly and slightly convex, surrounded by a narrow 

 margin. Glabella obsolete, indicated only posteriorly by the basal lobes, which are 

 small. 



Thorax : axis faintly trilobed, pleuras short and grooved. 



Tail rounded, with narrow margin, gently convex. Axial furrows faintly 

 marked. Axis wide, divided into three segments, which are separated by rather 

 faint furrows. The first segment is wide and short; the second is narrower than 

 the rest, hexagonal in shape, slightly raised along the median line into a slight 

 keel which projects backwards over the posterior lobe; the posterior lobe is 

 elongated and terminates in a rather blunt point. The lateral lobes are nearly 

 uniform in width throughout and are confluent behind the axis. 



Head- and tail-shields about 7 mm. long and wide. 



