446 Dr. H. Hicks — Life Zones in Palceozoic Rocks. 



Soon after M. Barraade's conclusions had been announced, " Mr. 

 Salter was directed by Sir H. de la Beche to re-examine a portion 

 of the Lingula Flag series, with special regard to the fossil suc- 

 cession, and found, that the group was divisible into three distinct 

 zones, two in the Lower, and one in the Upper division." As 

 characteristic of the Lower series, he mentions Agnostns princeps, 

 Olenus cataractes, and LinguleUa Davisii, of the next overlying series, 

 Olenus micriirus, Hymenocaris vermicauda, and Lingullela Davisii in 

 great abundance ; of the highest, Olenus alatus, 0. scarabceoides, 

 Agnostus princeps, several species of Conocoryphe, Orthis lenticularis, 

 and Dictyonema ? sociale. In 1860 Mr. Salter again visited North 

 Wales, and with " the hearty and eager assistance of Messrs. 

 Homfray and Ash," and the services of the Chief Collector of the 

 Survey, Mr. E. Gibbs, was not only able to add to the number of 

 forms, but also to trace the three divisions into several new areas. 

 In 1867 Mr. T. Belt, in a paper on " Some New Trilobites from the 

 Upper Cambrian Kocks of North Wales," ^ subdivides the lowest 

 series given by Mr. Salter, and points out that there are two 

 horizons marked by distinct species of Olenus, Olenus gibbosus 

 being characteristic of the lowest, and Olenus cataractes of the 

 higher beds. In another paper, " On the Lingula Flags or Ffestiniog 

 Group of the Dolgelly district," ^ he gives the results of researches 

 carried on by him during the previous three years in conjunction 

 with Messrs. Ezekiel Williamson and J. E. Barlow, and says that 

 " recent discoveries have shown that the group includes at least six 

 zones of animal life, each distinct and separate." To the three 

 divisions previously marked out by Mr. Salter he gives the local 

 names of Maentwrog, Ffestiniog, and Dolgelly, and says that they 

 " are both lithologically and palgeontologicaliy distinct. None of 

 the Crustaceans pass from one group to another, and peculiar genera 

 are found in each." Professor Phillips had previously discovered 

 several species of Olenus in black shales on the western flanks of 

 the Malvern Hills, and these beds Mr. Belt correlates with his 

 Upper Dolgelly beds. Other fossils had been discovered in these 

 rocks, near Malvern, by Dr. Harvey B. Holl, Dr. Grindrod, the 

 Eev. W. S. Symons, and others. In the year 1877 Dr. C. Callaway 

 published a paper,^ in which he gives an account of a most 

 interesting discovery by him of Upper Cambrian rocks in South 

 Shropshire. The " Shineton shales," he there states, appear to him 

 from the fossils to be of Tremadoc age ; but he says that one new 

 species of Olenus (0. Salteri) "is probably representative of our 

 Lingula Flags," and also that the majority of the "species have an 

 older facies than the Tremadoc ; but the abundant occurrence of an 

 Upper Tremadoc form, and of another Asaphid, points in an opposite 

 direction." He then states "that the facts of the case so far as 

 the fossils are concerned will be best satisfied by referring the beds 

 to the age of the Lower Tremadoc," but suggests the probability 

 of the " Shineton shales forming beds of passage between the 



1 Geol. Mag. Vol. IV. p. 294. ^ jjj^;. p. 493. 



^ Quart. Journ. Geol. Soc. Tol. xxxiii. p. 652. 



