444 Dr. H. Hides — Life Zones in Palceozoic Rocks. 



beds. In my paper in the Quart. Journ. Geol. Soc. in 1872, after 

 giving a minute description of the strata from the base of the 

 Cambrian to the Lingula Flags and the evidences of the physical 

 conditions under which they had been deposited, I added the 

 following remarks : " These successive changes, producing such 

 varied conditions of deposit, must have had much to do with 

 causing barrenness in parts of the sti-ata, and with the appearance, 

 on the other hand, of successive zones of animal life. The con- 

 tinuation of the same genera through a great thickness of shore or 

 shallow- water deposits, as is the case in the Longmynd (now called 

 Caerfai and Solva Groups) and Lingula Flags and the rapid 

 dying out and shorter range of the genera in finer beds or deep 

 sea-deposits, like the bulk of the Menevian Group, ai'e interesting 

 facts, and deserving of consideration when we seek for natural 

 laws to account for the- conditions presented to us at these early 

 periods." Though a considerable number of the St. David's species 

 have been found in North Wales in beds almost identical in character 

 with those at St. David's, two species only of Paradoxides, viz. 

 P. Hichsii and P. Davidis, have as yet been determined. They hold 

 there exactly the same position in relation to one another as they 

 do at St. David's, and 1 have no doubt a careful examination of the 

 underlying beds will show that the Lower Zones occur there also. 

 Soon after we had discovered the majority of the forms at St, 

 David's, Mr. D. Homfray was asked by Mr. Salter to examine the 

 slaty beds which flanked the Harlech Mountains, and in a joint 

 paper by Mr. Salter and myself to the Geological Society ' Mr. 

 Salter gives the general results in the following words : " Having 

 faith in the continuity of the band, I had begged Mr. David Homfray, 

 of Portmadoc, to employ his first leisure in examining the same 

 horizon in the Ffestiniog country, a locality which had hitherto been 

 neglected. He met with his usual good success ; and found, not 

 merely the same genera, but many species which we had discovered 

 at St. David's. I think hardly any of the forms are distinct. There 

 are Anopolenus, Conocoryphe, Microdiscus, HolocepJialus, together with 

 Theca and Agnostiis, all, or nearly all, of the same species as those 

 described in our paper. There is also a new genus of Trilobites 

 which we have called Erinnys, distinguished by the great number 

 of the body-rings, and this is also found both in North and South 

 Wales. This identity of forms between localities so widely 

 separated and on the same horizon gives us great reason to 

 believe that the fauna is a marked and persistent one over large 

 areas." In 1891 (Geol. Mag. p. 533) Prof. Lap worth announced 

 the discovery by Mr. T. T. Groom of a Paradoxides occurring with 

 Ptychoparia, Obolella, Protospongia, etc., at Nevis Castle and Comley, 

 Shropshire. In a paper in 1875 in which I attempted to correlate 

 the main zones which we had found in Wales with those which had 

 at that time been made out in various areas on the Continent of 

 Europe ^ I said that the " Western areas have a larger number of 



1 Quart. Journ. Geol. Soc, November, 1865. 



- ' ' The Physical conditions under which the Cambrian and Lower Silurian rocks 

 ■were probably deposited over the European areas" (Q.J.G.S. Yol. xxxi. p. 552). 



