from the Fossiliferous Limestone of Durham. 321 



sequently it is pre-eminently characteristic of Permian deposits. 

 Associated with the species belonging to the abov^e groups are a 

 few forms which have been referred to Cythere, Cythereis, and 

 Cytherella, all of which, with one exception, are found in the 

 upper Permian beds of Byers^ Quarry, and some of which also 

 occur in the Lower Zechstein of Germany. In the former beds 

 these forms are in the ascendant, being seven in a list of twelve 

 species found therein. The difference in generic affinity observed 

 in the species of these beds from those found in the fossiliferous 

 limestone, which almost occupies the same area of distribution, 

 may be indicative of peculiar conditions. It is generally assumed 

 by geologists of Permian repute, that the upper beds of Durham 

 oi'iginated in comparatively shallow water; nor is it an unwar- 

 rantable assumption, as some of the beds are ripple-marked*, 

 and in others there are found occasionally the remains of Algsef, 

 — facts which certainly do not imply any great depth of water. 

 So, supposing littoral conditions to have prevailed during their 

 period of deposition, the differences obser\ed in the generic 

 relations of the species may, in some measure, be due to them ; 

 and the Byers' Quarry group of Entomostraca may represent 

 some of those species which loved a habitat of shallow depths in 

 this Permian age ; while in those found in the fossiliferous 

 limestone, which belong so exclusively to Bairdia, we may possess 

 a group of pelagic species which dwelt in the waters of a Permian 

 ocean. Although this is advanced as a mere suggestion, so far 

 as evidence is derivable from the species in question, yet it is an 

 idea which is supported by many collateral facts that may be 

 deduced from the general fauna of this deposit. 



The list of Permian Entomostraca is now rather extensiv^e. 

 Twelve species were described by Jones in 1850. In this paper 

 six new forms will be noticed, besides three previously dis- 

 covered in Germany, but new to Durham ; so that, in all, the 

 Permians of Durham will possess a list of twenty-one species, 

 thirteen of which are peculiar to them. Eight species appear 

 to be common to the deposits of Germany and Durham, some of 

 which have existed from the deposition of the Lower Zechstein, 

 the equivalent of our compact limestone, until the last of the 

 Permian beds were accumulating. Five species are peculiar 

 to Germany; and six have been found in Russia, which are as 

 yet unknown in the West. These, with the British s])ecies, 

 make thirty-two species of Entomostraca belonging to the 

 Permian strata of Europe. 



* Prof. King observed ri|)plc-marks in the upper yellow limestone on the 

 site of the South Docks, Sunderland ; and I have also seen slabs marked 

 with them in the Fuhvell Quarries. 



t From the upper liraestoue beds between Hawthorne Hive and Black 

 Hall Rocks on the Durham coast. 



