﻿1861.] 



KIEKBT PEEMIAN, SOUTH YORKSHIRE. 



317 



absences, that of Brachiopoda being the most notable. In the most fos- 

 siliferous localities in Durham, Brachiopods are the commonest fossils. 

 In Yorkshire the only species of this class that occurs is almost among 

 the rarest. The two common Polyzoans of Durham — Fenestella reti- 

 formis and Synocladia virgulacea — are also wanting, their places being 

 apparently taken by Acanthocladia anceps. The commonEchinoderm 

 of Durham is absent, as are also other species too numerous to name, 

 several of which are common forms in the Durham beds. On the other 

 hand, Nautilus Freieslebeni, Chemnitzia Roessleri, Straparollus Per- 

 mianus, Chiton Loftusianus, Monotis speluncaria, Macrodon striatus, 

 Terebratula elongata, Acanthocladia anc&ps, Retepora Ehrenbergi, 

 Miliola pusilla, as well as others that are common to both fauna?, and 

 which in Durham and Germany are confined to the lower and middle 

 subdivisions, form a most intimate relationship between the two, and 

 afford strong palseontological evidence — were any wanting — of the 

 inferior position in the series of the deposits containing the Yorkshire 

 group of species. 



But to form a just comparison with the Durham fauna, we must 

 take it as developed during the deposition of the Compact Limestone, 

 the equivalent — in great measure — of the Lower Limestone. But 

 before doing this, it may again be pointed out that the fossils of the 

 Compact Limestone do not represent the earliest traces of Permian 

 life in Durham, as do those of the Lower Limestone in Yorkshire. 

 In the latter county the deposition of the Lower Bed Sandstone or 

 Bothliegendes was immediately followed by that of the Lower Lime- 

 stone ; at least there was no intermediate deposition. In Durham a 

 deposit of semicalcareous, semiargillaceous sediment followed that 

 of the Rothliegendes, and preceded that of the Compact Limestone 

 — thus separating the two deposits by a few feet of calcareous shale, 

 which has been named the Marl-slate. It was during the deposi- 

 tion of this shale that animal life may be said to have first appeared 

 in the Durham area during Permian time, — Lingula Credneri, Dis- 

 tinct KonincM, and Myalina Hausmanni, with several Fishes, forming 

 this avant-garde of the larger fauna that afterwards peopled the 

 same area. I have little doubt that these species were contempora- 

 ries with those of the fauna of the Lower Limestone, though only for 

 a season ; for on the commencement of deposition of the Compact 

 Limestone, another set of species gradually took their place, and be- 

 came in turn contemporaries of the same Yorkshire species, which 

 continued to people the Yorkshire area while the changes noticed 

 were occurring in Durham. And it was not until the era of the 

 Compact Limestone that the physical conditions of the Durham area 

 became analogous to those prevailing in the area of Yorkshire, and 

 that the distribution of species therein became, like those of York- 

 shire, of an unquestionably marine character. It is, therefore, 

 chiefly with them that we have to do in comparing the contem- 

 porary faunae of the two districts. 



As far as we are acquainted with the fossils of the Compact Lime- 

 stone, they amount to 31 species, thus forming a group of equal num- 

 ber with those of the Lower Limestone. A list of these species is 



