214 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 21, 



Magnesian Limestone of Durham, together with remarks on some 

 other Permian fossils. 



1. Prosoponiscus problematicus, Schlotheim, sp. 

 PI. VII. figs. 1-7. 



Trilohites jprohlematiciis, Schlotheim, Petrefact. 1820, p. 41. 

 Palceocrangon problematical Schauroth, Zeitschr. deut. geol. Ge- 

 sell. 1854, vol. vi. p. 560. pi. 22. figs. 2 a-e. 



In the summer of 1853 I found two imperfect specimens of one 

 of the higher (malacostracan) Crustaceans in the limestone at Hum- 

 bleton Quarry. At the time I thought that the species belonged to 

 the Macrura ; but I now find this was an error. A short notice of 

 this interesting discovery appeared in the Address of the President 

 of the Tyneside Naturalists' Field Club, March 15, 1854 *. 



At that time I believed that none but the lower forms of Crusta- 

 ceans had been previously found in the Permian rocks. I have since 

 learned, however, that in Schlotheim's ' Petrefactenkunde,' 1820, 

 p. 41, mention is made of the discovery (in the Zechstein-dolomite 

 of Gliicksbrunn) of a peculiar fossil, named by Schlotheim Trilobites 

 pi'oblematicus, which is probably the same species as mine. 



In 1854 Baron Schaurothf authenticated Schlotheim's discovery, 

 and figured and described a specimen of this species as belonging to 

 one of the higher groups of Crustacea, naming it PalcBocra7igon 

 problematica. On comparing my specimens with the figures given 

 by Schauroth, I have a little hesitation in regarding them as belonging 

 to the same species ; but as " Palseocrangon " does not express the 

 affinities of the fossil animal, I propose, as a more correct generic 

 term, the name Prosoponiscus f, as suggested by a palaeontological 

 friend. 



Though my original specimens are in no respect inferior to those 

 of Schauroth' s, I did not venture to name and describe them when 

 they were first noticed, but postponed doing so in the expectation of 

 procuring more examples, and obtaining a more definite knowledge 

 of the affinities of the species. It was not, however, until the sum- 

 mer of the present year that any further traces of it were found, 

 when one or two other fragments from a different locality were met 

 with. In all, six specimens have been obtained : two from Humble- 

 ton Quarry, three from Field House, Ryhope, and one from Tun- 

 stall Hill. 



Drawings of the most perfect of these have been submitted to Mr. 

 C. S. Bates, and I am indebted to that gentleman for the following 

 interesting remarks : — 



*' There is but one Order among recent Crustacea with which 

 figs. 1 and 2 can be identified, and that is the Isopoda. But the 

 relation of the fossil to the recent species is peculiar. In all recent 

 forms (as far as I know) where the eyes project upon the surface of 



* Transactions of the Tyneside Nat. Field Club, vol. ii. p. 333. 



t Zeitschrift der dentsch. geolog. Gesell. vol. vi. p. 560. pi. 22. fig. 2. 



X From Trpoo-wTTov, a face or mask, and 6vi(yKo<s, oniscus. 



