NORTnUMBERLAjSrn AND DURHAM. 17 



are remains of what he considers a minute air-breathing Batra- 

 chian, with teeth like those of Dendrerpeton and the frog, and 

 which he has named Gastrodus propositus. Associated with fish- 

 remains are usually numbers of Entomostraca {Beyrichia arcuata, 

 and Cytheropsis Scoto-Burdigalensis), which appear to have acted 

 like scavengers in the carboniferous waters, clearing away the 

 decomposing flesh of the fish. Remains of insects, nearly allied 

 to the genus Blatta, have been detected by Mr. Xirkby in an 

 ironstone band, near the top of the Coal Measures, on the north 

 bank of the "Wear, opposite Claxheugh. Plants, however, are 

 the distinguishing organisms of the Coal Measures ; they had 

 grown in vast abundance on the ancient swampy ground of the 

 Carboniferous era, and they supplied the material which forms 

 the coal beds. A few coniferous trees flourished at this era, 

 and the following species have been determined : Picea Withami, 

 Pinites amhigua and anthracina, Dadoxylon approximatus and 

 Brandlingi ; but the most abundant plants are Sigillarm, of 

 which thirteen species have been noticed ; and they appear to 

 have furnished a large proportion of the vegetable matter form- 

 ing coal, since their roots, the Stigmaria ficoides, are in great 

 numbers in the clay underlying each coal seam. Of Lepido- 

 dendra there are eleven species, and of Calamites seven. Fronds 

 of ferns were in great profusion, and of these fifty species have 

 been recorded, though probably not a few have been determined 

 from different parts of the same plant. 



The Carboniferous system has been uplifted and dislocated at 

 different periods. The last upheaval of the Cheviots tilted up 

 the lower strata ; and the basaltic protrusions of a later time 

 produced considerable disturbance. Eut the effects of the greatest 

 elevating force affecting our district are seen in the Penine chain, 

 extending from Tindale Pell southward about 60 miles; for along 

 this line of mighty fracture the Mountain Limestone beds on the 

 east side have been thrust upward, in some parts, near to 3000 

 feet — and this stupendous mountain wall rises some 2500 feet 

 above the New Eed Sandstone plain lying on the west. The 

 Stublick and the Ninety-fathom Dikes are probably secondary 

 effects of this disruption. By the Ninety-fathom Dike, which 



