PALEOZOIC TIME — CAMBRIAJiT. 



481 



ford, County of Wicklow. Other reported regions, partly metaniorphic, are 

 those of Charnwood Forest, and the Western Highlands of Scotland. 



The lower part of the Cambrian of St. Davids is divided by Dr. Hicks 

 into (1) the Caerfai group, (2) the Solva, and (3) the Menevian. The 

 Lower Cambrian includes (according to Walcott) the first of these groups ; 

 it contains Lingulella primceva, L. ferruginea, Discina Caerfaiensis, Leperditia 

 Camhreyisis, but no Olenellus has been reported. To it, as Lapworth shows, 

 belong also sandstone beds in Shropshire, from which he has described 

 Olenellus Callavei (with which occur species of Kutorgina, Acrothele, etc.). 

 There are there no overlying Paradoxides beds. Here belong also the 

 sandstones, flags, and slates of Bangor and Llanberis, toward the Menai 

 Straits. 



The Middle Cambrian or Paradoxides section comprises the Solva and 

 Menevian beds of St. Davids, which have afforded Paradoxides Harknessi, 

 P. Solvensis, P. Davidis, with Protospongia fenestrata and species of Lingidella, 

 Theca or Hyolithes, Discina, Ortliis (OrtJiisina), Stenotheca, Agnostus, Micro- 

 discus, Conocoryphe, Lejyerditia. The Lower Cambrian and part of the 

 Middle of Sedgwick are here included. 



The Upper Cambrian or Olenus division comj)rises the Lingula flags and 

 Tremadoc slates, which occur along by Maentwrog, Festiniog, and Dolgelly 

 in ISTorth Wales, and the Tremadoc beds both in North Wales and at St. 

 Davids. 



The genus Olenus here has its largest development. The beds include 

 also Dictyonema, and other Graptolites ; species of Lingulella, as L. Da- 

 visi (Fig. 591), Lingula, Obolella, Kutorgina, Orthis; Hyolithes, Conularia, 



Fig. 589, Oldhamiaantiqua; 590, O. radiata; 591, Lingulella Davisi; 592, Agnostus Rex; 593, 

 Olenus micrnrus ; 594, Sao hirsuta (i) ; 595, Hymenocaris verraicauda (i). 



Bellerophon (B. Cambrensis) ; among Trilobites the genera Agnostus, Cono- 

 coryphe, Ampyx, Olenus (among the many species. Olenus micrurus. Fig. 593), 

 Dicellocephalus, Sphcerophthalmus ; also the Crustacean Ostracoids, Leper- 

 ditia, Primitia ; the Caridoid species, Hymenocaris vermicauda (Fig. 595). 

 In the Tremadoc slates occur several species of Graptolites ; Dendrocrinus 

 Cambrensis and Palceaster, among the earliest Echinoderms ; Lamellibranchs 

 of the genera Modiolopsis, Palcearca, Ctenodonta, etc. ; Pteropods of the genera 

 TJieca and Conularia; the earlier of British Cephalopods, of the genera Ortho- 



DANA'S MANUAL- 



^1 



