262 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 22, 



dips slightly to the east, and, commencing at the western extremity 

 of the region, either soon thins out or is lost under the more recent 

 accumulations of the tertiary period. It has never been observed in 

 the sections or quarries near Mayence, nor does it occur on the right 

 bank of the Rhine. It may be said to be confined to a small tract 

 of country in the neighbourhood of Weinheim, near Alzey, and 

 about Fiirfeld, Uff hofen, Flonheim, and a {ew other localities in that 

 region ; it may also be occasionally traced in small patches along the 

 hill-range to the south towards Diirckheim and Neustadt, but with- 

 out fossils, vpith the exception of a small spot near Diirckheim, 

 underlying the Cerithium-hmestone, where I found a bed of Pinnce, 

 which, however, were difficult to extract. They lie in a white and 

 incoherent sand, and the shells are generally as incoherent and 

 friable as the sand itself, with the exception of a few small masses 

 cemented together by a more calcareous matrix. This is, I beheve, 

 the only locality where Pinna has been found in this formation. 



Associated with this Pinna-sand is a bed of red ferruginous clay, 

 containing large septaria, but I was unable to ascertain the relative 

 position of the two beds in consequence of the broken nature of the 

 ground, and their not occurring in the same section. Both are, 

 however, below the Cerithium-limestone, and the section seen near 

 Beckenheim affords, I have no doubt, the true explanation of their 

 occurrence, viz. that the Pinna-sand represents the marine sands : 

 and the clay with septaria, the lower brown-coal formation or Cyrena- 

 marl. 



The two sections of the true marme formation in the vicinity of 

 Weinheim, near Alzey, are so much more important in respect of 

 their fossil contents than any others in this formation, that a more 

 detailed notice of them is perhaps necessary. The first locahty, 

 fig. 6, is on the high road, a few hundred yards to the E. of Wein- 

 heim. The rocks here form a low broken escarpment, serving as 

 the northern boundary of a small valley, watered by the stream 

 which flows through Alzey. On the south the ground rises gradually 

 over the undulating hill of the Sommerberg to the general table- 

 land of the country, which consists of the overlying Cerithium-lime- 

 stone. The marine beds themselves dip very shghtly to the E. and 

 S.E., and on approaching the village of Weinheim they are seen 

 reposing directly on a dark greenish trappean rock. 



Such igneous rocks, it may be here observed, are very abundant 

 throughout this district, particularly towards the Donnersberg, and 

 in the direction of Kreuznach, appearing as porphyry, melaphyr, or 

 greenstone, and frequently containing geodes of agate and tabular 

 veins of chalcedony. Sometimes they have cut through the under- 

 lying red or carboniferous sandstone, at others they have only caused 

 the elevation of the sedimentary rocks, but they are all anterior to 

 the deposition of the tertiary beds. 



The section, fig. 6, represents the general appearance of the beds 

 opposite the Wirthsmiihle. A hard bed of compact limestone rests 

 rather irregularly against the trap-rock. It contains a few remains 

 of Ostrea, Pectuncufas, kc. Over it is a loose shellv sand, 3 or 4 feet 



