No. 3.] HUNT — ON CAMBRIAN AND SILURIAN. 301 



by Messrs. Harkness and Hicks, whose paper on the Ancient 

 Rocks of St. David's Promontory appears in the Geological 

 Journal for November, 1871. [XXVIII, 384.] The Cam- 

 brian sediments here rest upon an older series of crystalline stra- 

 tified rocks, described by the geological surveyors as syenite and 

 greenstone, and having a north-west strike. Lying unconformably 

 upon these, and with a north-east strike, we have the following- 

 series, in ascending order : 1. quartzosc conglomerate, 60 feet ; 

 2. greenish flaggy sandstones, 460 feet; 3. red fl.igs or slaty beds, 

 50 feet, containing Ling nlella ferruginea^ besides a larger species, 

 Discuia, and LepercUtia Camhrensis ; 4. purple and greenish 

 sandstones, 1000 feet; 5. yellowish gray sandstones, fl igs and 

 shales, 150 feet, with Plutonia, Conoconjphe^ Mlcrodiscus, 

 Agnosfiis, Theca and Protospongia ; 6. gray, purple and red 

 flaggy sandstones, with most of the above genera, 1500 feet; 7. 

 gray fliggy beds, 150 feet, with Paradoxides; 8. true Menevian 

 beds, richly fossil iferous, 500 feet. The latter are the probable 

 equivalent of the base of Barrande's Etage C, and at St. David's 

 are conformably overlaid by the Lingula-flags ; beneath which we 

 have, including the Menevian, a conformable series of 3370 feet 

 of uncrystalline sediments, fossiliferous nearly to the base, and 

 holding a well-marked fauna distinct from anything hitherto 

 known in Great Britain or elsewhere. 



The Menevian beds are connected with the underlying strata 

 by the presence of Lingidella ferrugiuea, Disclna pileolus, and 

 OholeUa sngittatis, which extend through the whole series ; and 

 also by the genus Paradoxides, four species of which occur in 

 these lower strata ; from which the genus Olenua, which charac- 

 terizes the Lino-ula-flao-s. seems to be absent. To a large tuber- 

 culated trilobite of a new genus found in these lowest rocks the 

 name of Plutonia Sedgwickii has been given. Hicks has proposed 

 to unite the Menevian with the Harlech beds, and to make the 

 summit of the former the dividing line between the Ijower and 

 Middle Cambrian, a suggestion which has been' adopted by Lyell. 

 [Proc. Brit. Assoc, for 1868, p. 68, and Lyell, Student's Manual 

 of Geology, 466-469.] 



Both Phillips and Lyell give the name of Upper Cambrian 

 to the Lingula-flags and the Tremadoc slates, which together 

 constitute the Middle Cambrian of Sedn-wick, and concede the 

 title of Lower Silurian to the Bala group or Upper Cambrian 

 of Sedgwick. The same view is adopted by Linnarsson ia 



