H. C. Sorby, H. Hicks 313 



is true, but still revealing a definite order of succession among 

 the varieties of lithological character. There are there older 

 granitoid masses succeeded by overlying volcanic series. 

 Dr. H. Hicks (1837-1899), a young local medical practitioner, 

 attacked this difficult problem in the latter half of the 

 nineteenth century, and gave the latinized local names of 

 Dimetian and Pebidian to the two principal divisions. Pro- 

 fessor Bonney, E. B. Tawney, and others soon took up the 

 work and were in time able to draw up a sketch of the history 

 of that early metamorphic series. Similar rocks were dis- 

 covered elsewhere in the same position with reference to the 

 fossiliferous formations and, though differing in details, were 

 easily co-related with the typical series of St. David's. These 

 had been noticed by earlier stratigraphical geologists, but 

 were passed over with only a short description. There was, 

 however, little doubt about the Archaean Rocks (as they 

 came to be called) of North Wales, of the Midlands, where 

 they have been described by Callaway and others, and of 

 North-West Scotland, where a new difficulty was introduced 

 by the wondrous earth movements which left these as well as 

 some newer rocks folded, broken, displaced, and crushed, 

 often beyond recognition. The researches of Dr. Hicks and 

 his able exposition of his progressive views on the Archaean 

 Rocks are sufficient to prove what geologists owe to the 

 accident of his residence at St. David's; but there was yet 

 more left for him to discover. Resting upon the denuded 

 surface of the Archaean Rocks were the Basement Beds of 

 the Cambrian separated from the pre-Cambrian Rocks by 

 a vast interval of time. The Survey had passed over the 

 district without detecting any trace of fossils in these beds, 

 but Hicks resided there, and his hammer left little untried. 

 He found fossils in these early Cambrian beds and, incited 

 to closer search, he found them in lower and lower beds till 

 there was hardly any horizon from which he had not pro- 

 cured new species and new genera. This brought Salter, 

 one of the most acute of palaeontologists, to his side. These 

 unexpected discoveries are recorded in the name given to a 

 trilobite, seventeen inches long, which was called Paradoxides 

 Davidis, the specific name connecting it with St. David's. 

 The subdivisions in which these various forms occurred 



