Prof. T. Sterry Sunt — On Cambrian and Silurian. 457 



the fixing by Sedgwick of their geological horizon, was at once 

 followed by a careful examination of them by the Government Sur- 

 veyors, and in 1847 Selwyn detected in the Lingula-flags, near 

 Dolgelly, in Merionethshire, the remains of two crustacean forms, 

 the one a Phyllopod, which has received the name of Hijmenosaris 

 vermicaiida, Salter, and the other a trilobite which was described by 

 Salter in 1849 as Olenus micrurus. (Geol. Survey, Decade ii.) A 

 species of Faradoxides, apparently identical with P. Forclihammeri of 

 Sweden, was also about this time recognized among specimens sup- 

 posed to be from the same horizon. It has since been described as 

 P. Hicksii, and found to belong to the basal beds of the Lingula- 

 flags, — the Menevian group. 



Upon the flanks of the Malvern Hills there are found resting upon 

 the ancient crystalline rocks of the region, and overlaid by the Pen- 

 tamerus beds of the May Hill Sandstone (originally called Caradoc 

 by Murchison) a series of fossiliferous beds. These consist in their 

 lowest part of about 600 feet of greenish sandstone, which have 

 since yielded an Obolella and SerpuUtes, and are overlaid by 600 feet 

 of black schists. In these, in 1842, Prof. John Phillips found the 

 remains of Trilobites, which he subsequently described, in 1848, as 

 three species of Olenus. (Mem. Geol. Survey, vol. ii. part 1, p. 55.) 

 These black shales, which had not at that time furnished any organic 

 remains, were by Murchison in his Silurian System (p. 416) in 1839 

 compared to the supposed Passage-beds in Caermarthen shire between 

 the Llandeilo and the Cambrian (Bala) rocks; which, as we have 

 seen, were newer and not older strata than the Llandeilo-flags. From 

 their lithological characters, and their relations to the Pentamerus 

 beds, these lower fossiliferous strata of Malvern were subsequently 

 referred by the Government geologists to the horizon of the Caradoc 

 proper or Bala group ; nor was it until 1851, that their true geo- 

 logical age and significance were made known. In that year Bar- 

 rande, fresh from the study of the older rocks of the continent, came 

 to England for the purpose of comparing the British fossils with 

 those of the Primordial Zone, which he had established in Bohemia 

 and Scandinavia, and which he at once recognized in the Lingula- 

 flags of Sedgwick and in the black schists at Malvern ; both of which 

 were characterized by the presence of the genus Olenus, and were 

 referred to the horizon of his Etage C. This important conclusion 

 was announced by Salter to the British Association at Belfast in 

 1852. (Eep. Brit. Assoc, Abstracts, p. 5Q, and Bull. Soc. Geol. de 

 Fr., ser. ii. vol. xvi. p. 537.) Since that time the progress of in- 

 vestigation in the Middle and Lower Cambrian rocks of Wales has 

 shown a fauna the importance and richness of which has increased 

 from year to year. 



The paleeontological studies of Salter, while they confirmed the 

 primordial character of the whole of the great mass of strata which 

 make up the Middle Cambrian or Ffestiniog group of Sedgwick 

 (consisting of the Lingula-flags and the Tremadoc slates), led him 

 to propose several sub-divisions. Thus he distinguished on paleeon- 

 tological grounds between the Upper and Lower Tremadoc slates, and 



