CXXXVm PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Irish Olhamia, — that the characteristic type of organization of the 

 Silurian epoch had aheady manifested itself. 



Mr. Salter also proposed to form a new genus for that remarkable 

 form of Cephalopoda described by Sowerby as Orthoceras bisiphona- 

 tum, and figured in the " Silurian System/' and in " Siluria." In this 

 form ordinary septa are pierced by an excentric-beaded siphuncle, 

 alongside of which a deep lateral cavity passes down, affecting at 

 least seven, if not more, of the septa. Though the character of the 

 shell may be elucidated by the structural peculiarities of Orthoceras 

 paradoxicum, and of Gonioceras, its real affinities are, in Mr. Salter's 

 opinion, with Ascoceras and Ccuneroceras. So great a peculiarity of 

 structure appears to justify the formation of a new genus, although 

 the object of the lateral cavity has not been satisfactorily explained : 

 Mr. Salter has, therefore, called it Biploceras. Mr. Salter noticed 

 also a new species of Ascoceras from Ludlow, under the name of 

 A. Barrandii, the genus itself being new to Britain. 



Mr. Salter and Mr. W. H. Baily gave a list of the fossils found 

 in the chalk-flints and greensand of Aberdeenshire, notices of which 

 have been already published in other journals. The fossils are those 

 characteristic of the upper greensand, but the Lima elegans of Nilsson, 

 found, in association with the ordinary Inocerami and Echinites of 

 the chalk, in the rolled flints which form terraces round the hills in 

 Aberdeenshire, is new to Britain, and affords therefore some reason for 

 suggesting a former continuity of these beds with those of the south 

 of Sweden . In Ireland I have shown that the basalt in one locality rests 

 upon a bed of flints, which is there the only representative of the cre- 

 taceous formation ; but so great must be the difficulty of deducing 

 any certain result from materials which have undergone so much 

 wear as these flints^ that I should hesitate to draw so large a conclusion 

 as the former continuity of the Scotch and Swedish beds, though I 

 should come to another, perhaps equally important, namely that the 

 climatal and other conditions of the Scotch and Swedish areas were 

 at the cretaceous epoch so similar as to produce a close resemblance 

 between their respective faunae. 



Mr. J. W. Kirkby, in a communication made through Mr. David- 

 son, notices the occurrence of a minute Malacostracous Crustacean in 

 the magnesian limestone of Durham. It appears to be the same as 

 the Trilohites prohlematicus of Schlotheim, and Palceocrangon pro- 

 blematica of Schauroth ; but, in the opinion of Mr. C. Bates, it is 

 nearly related to the Isopoda, and represents their immature rather 

 than their mature form. Every recognition of a recent type of 

 structure in these ancient rocks is of interest, as tending to break 

 down the abrupt organic barrier, supposed, most probably with 

 little reason, to separate geological formations. Amongst the other 

 fossils noticed, was a new species of Chiton, C. Howsianus. 



Mr. S. P. Woodward described the appearance of some Orthoce- 

 rata as exhibited in polished slabs of limestone brought by Mr. 

 Lockhart, from Shanghae, in China, but supposed to have been 

 brought from some place 200 miles distant, where they appear to 

 have been used as screens, having been mounted in wooden frames. 



