PLATE III. 



FlCr. PACE. 



Agnostus incertus, Brogger. 29 



1,2. Heads. Cambrian; Neves Castle. Collected by Mr. Rhodes. Geological Survey, 



E. R. 2453 (fig. 1), R. R. 2446 (fig. 2). 

 :!. Tail. Cambrian ; Neves Castle. Collected by Mr. Rhodes. Geological Survey, R. R. 2455. 



Microdiscus lobatus (Hall). 32 



I- <;. Heads. Cambrian; Comley. Collected by Mr. E. S. Cobbold. Sedgwick Museum. The 

 specimen represented in fig. 4 shows two furrows across the glabella in front of the 

 occipital furrow ; in the other two specimens no such furrows are visible. Fii;-. 5 a is a 

 side view of the specimen represented in fig. 5. 



Microdiscus speciosus, Ford. 33 



7. Head. Cambrian ; Comley. Collected by Mr. E. S. Cobbold. Sedgwick Museum, 



Microdiscus, sp. 34 



8. Tail. Olenellus zone; Comley Quarry. Collected by Mr. E. S. Cobbold. Sedgwick 



Museum. 



Microdiscus sculptus, Hicks. 35 



9. Hicks's type ; an entire but very poorly preserved specimen. Harlech Series; Nun's Well, 



St. David's. (Figured by Hicks, Quart. Journ. Geol. Soc, vol. xxvii, pi. \vi, tit;-. 9, 9 a.) 



10. Tail. Harlech Series ; Nun's Well, St. David's. Sedgwick Museum. (Figured bv Hicks, 



ibid., pi. xvi, fig. 10, 10 a.) 



Microdiscus punctatus, Salter. 36 



1 1 . One of Salter's figured specimens. An internal cast ; the neck-spine has been pressed 



down upon the thorax and has since been broken away ; its impression appears upon the 

 axial rings. Menevian ; Porth-y-rhaw, St. David's. Sedgwick Museum. (Figured by 

 Salter, Quart. Journ. Geol. Soc, vol. xx, pi. xiii, fig. 11 c.) 



12. Internal cast ; 12 a, side view of head of the same specimen. The neck-spine is broken off, 



but is restored in outline in the side view. Menevian ; near Nine Wells, St. David's. 

 Mr. G. J. Williams' Collection. 



13. Internal cast of head, showing in the surrounding matrix the impression of the upturned 



neck-spine. Menevian; Ihvrrhvd, near Solva. Oxford University Museum. 



14. Head. An artificial cast of a natural external mould. Except where a small portion of 



the test remains in the mould the margin is not crenulated. Menevian; near Nine 

 Wells, St. David's. Sedgwick Museum. 



15. Head of a young individual ; internal cast. Menevian ; near Nine Wells, St. David's. 



Sedgwick Museum. 



16. Tail and thoracic segments ; internal cast. Menevian ; near Nine Wells, St. David's. 



Sedgwick Museum. 



17. Tail, internal cast; 17 a, external mould of the same individual. The actual testis not 



present in either. Both are covered with tubercles, showing that the test itself was 

 punctate, or else perforate both internally and externally. Menevian ; Dwrrhvd, near 

 Solva. Oxford University Museum, 



Shumardia pusilla (Sars). 40 



18. Internal cast. Shineton Shales ; Shineton. Collected by Mr. Rhodes. Geological Survey, 



R. R. 2266. 



19. External mould. Shineton Shales ; Shineton. Collected by Mr. Rhodes. Geological 



Survey, R. R. 2282. 



20. Internal cast. Upper Tremadoc ; Amnodd Bwll, Arenig. Mr. G. J. Williams' Collection. 



The small outlines, filled in with a flat shade and placed by the side of the enlarged figures, 

 show the actual size of the specimens. 



