Ch. XXV.] 



LOWER CARBONIFEROUS STRATA. 



409 



there is a celebrated " bone bed," almost entirely made up of ichthyolites ; 

 and the same may be said of the " fish-beds" of Armagh, in Ireland. They 

 consist chiefly of the teeth of fishes of the Placoid order, nearly all of 

 them rolled as if drifted from a distance. Some teeth are sharp and 

 pointed, as in ordinary sharks, of which the genus Cladodus affords an 

 illustration ; but the majority, as in Psammodus and Cochliodus, are, 

 like the teeth of the Cestracion of Port Jackson (see above, fig. 288, p. 

 249), massive palatal teeth fitted for grinding. (See figs. 532, 533.) 



Fig. 532. 



Fig. 53.3. 



Psammodus porosus, Agas. Bone-bed, Mountain 

 Limestone. Bristol ; Armagh. 



Cochliodus contortus, Agas. Bone-bed, 

 Mountain Limestone. Bristol ; Ar» 

 magh. 



There are upwards of 70 other species of fish-remains known in the 

 Mountain Limestone of the British Islands. The defensive fin-bones of 

 these creatures are not unfrequent at Armagh and Bristol ; those known 

 as Oracanthus are often of a very large size. Ganoid fish, such as 

 Holoptychius, also occur ; but these are far less numerous. The great 

 Megalichthys Hibberti appears to range from the Upper Coal-measures 

 to the lowest Carboniferous strata. 



Foraminifera. — This somewhat important group of the lower animals, 

 which is represented so fully at later epochs by the Nummulites and 

 their numerous minute allies, appears in the Mountain Limestone to be 

 restricted to a very few species, the individuals, however, of which are 

 vastly numerous. Textularia, JVodosaria, Endoihyra, ri „ 53t 



and Fusulina (fig. 534), have been recognized. The 

 first two genera are common to this and all the after 

 periods ; the third has already appeared in the Upper Fusuiinu^/Undrica, 

 Silurian, but is not known above the Carboniferous ; 

 the fourth (fig. 534) is peculiar to the Mountain Lime- 

 stone, and is characteristic of the formation in the United States, Russia, 

 and Asia Minor. 



Magnified 3 diam. 

 Mountain Limestone. 



STRATA CONTEMPORANEOUS WITH THE MOUNTAIN LIMESTONE. 



In countries where limestone does not form the principal part of the 

 Lower Carboniferous series, this formation assumes a very different char- 

 acter, as in the Rhenish Provinces of Prussia, and in the Hartz. The 

 slates and sandstones called Kiesel-schiefer and Younger Greywacke 

 (Jungere grauwacke) by the Germans, were formerly referred to the 

 Devonian group, but are now ascertained to belong to the " Lower Car- 



