1869.] On a Ternary Geological Classification. 357 



Carboniferous, Permian, and Jurassic limestones. "With reference 

 to tins order I may liere quote an observation of Professor Eupert 

 Jones, "who says,* " Some of the dark-grey Carboniferous limestone 

 is as largely composed of FenesttUw, &c., as the Permian limestone 

 of Durham and Germany often is. One of the best instances of 

 Polyzoan limestone (representing the Faxoe and Maestrich chalk) 

 is the great white limestone of South Australia traversed by the 

 Murray river, and which occurs again, as it were, in New Zealand 

 as the Ototara limestone of Otago, &c." 



The Echinodennata, as represented principally by the Crinoidese, 

 have contributed very largely to the formation of the limestones of 

 the Carboniferous period, as well as, though in a smaller degree, 

 of those of the Upper Silurian and Jurassic periods. As the late 

 Professor Edward Forbes remarks, " Formerly they were amongst 

 the most numerous of the ocean's inhabitants, — so numerous that 

 the remains of the skeletons constitute great tracts of the dry land 

 as it now appears. For miles and miles we may walk over the 

 stony fragments of the Crinoideae ; fragments which were once 

 built up in animated forms, encased in living flesh, and obeying 

 the will of creatures amongst the loveliest of the inhabitants of the 

 ocean."t The Crustacea, as represented by the diminutive Ento- 

 mostraca, took a very important part in the formation of limestones, 

 as abundantly proved by Prof. Piupert Jones and Dr. H. B. Holl.j 

 In the " Caradoc Bala " hmestone of the Chair of Kildare they 

 largely occur, and, with other Paleozoic forms, are placed by these 

 authors under the generic name of " Primitise."^ Prof. E. Jones 

 states, " The Caradoc Bala limestone of Kildare swarms with them ; 

 80 does that of Keisley in Westmoreland ; so do the Upper Silurian 

 limestones (AVenlock chiefly) near Malvern, as shown by Dr. Holl ; 

 BO does the Upper Silurian limestone of Gothland remarkably. The 

 Dudley limestone is rich with BeyricMse ; the Upper Silurian lime- 

 stone of Beechy Island in the Arctic regions and the Lower Silurian 

 limestones of Canada (in the Calciferous and Trenton groups) either 

 abound with, or are made up of, them. In the Lower Helderberg^ 

 group of the New York State (Upper Silurian) there is a Leperditia 

 limestone, and in Eussia and Oesel Isle, Leperditiae make u]o at least 

 one of the limestones." || Prof. E. Jones and Mr. J. W. Kirkby, 

 together with Mr, John Young and other authors, have also shown 

 that these little crustaceans abound in the calcareous beds of the 

 lower Carboniferous series of Scotland .IT The part m nature played 



* In a letter to the author (1868). 



t ' British Star-fishes,' p. 2. 



X ' Annals and Mag. Nat. Hist.,' 1865-8. 



§ " On Palajozoic Bivalved Entomostraoa, &c.," ibid., July, 1868. 



II Letter to the writer (1868). 



\ ' Trans. Geol. Society of Glasgow,' vol. ii., part 2, p. 213 ; ibid., p. 155. 



