XXXVlll PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Boulonnais, which from their proximity are hkely to throw most 

 hght on those of our own country. 



The formations of Nassau are classed as follows : — 



1. Posidonomya-shales, characterized by Posidonomya aciiticosta 

 and containing also eleven species of plants, some of which are found 

 in the coal-measures, of these Catamites transitionis and Stigmaria 

 ficoides deserve especial mention. The authors regard this bed as 

 the base of the coal-measures and as superior to the mountain-lime- 

 stone ; they know of no equivalent to it in France or Belgium, but 

 consider it identical with the shales containing Posidonomya near 

 Barnstaple in North Devon, and Launceston in Cornwall ; the Posi- 

 donia Becheri^ P. tuberculataf and P. lateralis of Sowerby and 

 Phillips being considered varieties of Posidonomya acuticosta, 

 Sandb. ; in this last view, I fully coincide, as I believe that the 

 varieties of form which led to an attempt to form these species are 

 due to distortion, but I do not think that the earliest name, P. 

 Becheri, should be abandoned. 



2. Cypridina-shale characterized by an abundance of the little 

 Gypridina serrato-striata : these beds also contain many species of 

 Goniatites and Orthoceras, the Clymenia subnautilina, and remains of 

 fishes, of which some may perhaps belong to the genus Holoptychius : 

 ten of the species of this formation are also found in the Eifel-lime- 

 stone. Its supposed equivalents are the Clymenien-kalk of Thuringia, 

 Saxony, &c. ; the Cucullsea-sandstone of Marwood, North Devon ; 

 the Petherwin-beds of Cornwall, and the shales containing Cypridina 

 above the limestone of Chimay in Belgium, &c. 



3. Stringocephaliis-limestone, in which 171 species of fossils have 

 been found, of which certain species of corals and Stringocephalus 

 Burtini (^under the new name of S. Mans) are most characteristic ; 

 6 of these species occur in the mountain-limestone, 1 in the Ortho- 

 ceras-slate, 2 in the Spirifer-sandstone, and 3 in the Silurian system. 

 The species common to this formation and to the Eifel-limestones of 

 Paffrath, Bensberg, and the Eifel, and to the lim.estones of Torquay 

 and Plymouth, are so numerous as to connect these deposits together 

 most satisfactorily : the authors also connect with it the limestone 

 of Chimay in Belgium, which contains 18 species in common with it, 

 among which is the String ocephalus ; though other species found at 

 Chimay might induce us to place that limestone somewhat higher in 

 the series. 



4. Orthoceras-slates of Wissenbach, &c., a blue roofing-slate, with 

 some beds of dark bituminous limestone, in which the shells are usually 

 in iron pyrites and sometimes in lead ore ; it abounds in species of 

 Orthoceras and Go7iiatites, of the former of which genera there are 

 two Silurian species. This bed has not been recognized out of Ger- 

 many. 



5. Spirifer-sandstone^ usually a fine sandstone or sandy slate, with 

 some rare beds of clay-slate, indicating, as there are no conglome- 

 rates, a deposit in a deep sea far from the coast ; 57 species of fossils 

 are enumerated, of which Spirifer macropterus and S. auriculatus, 

 Chonetes sarcinulata, and Ptilodictyon problematicum are considered 



