320" M. BouE' on 



commonly compact and grey, and of a peculiar crystalline 

 aspect, which is scarcely again found but in some beds of 

 the oolite formation ; it is occasionally rendered sublamellar 

 by means of spathose organic remains. 



The shells of this limestone are either petrified or in casts : 

 their petrifaction is commonly calcareous and rarely siliceous, 

 which is sometimes the case, as for example near Saarbruck. 

 The shelly beds occur very generally, yet we may mention 

 those of Mont Ileimberg, near Gottingen, that of the envi- 

 rons of Walterhausen and Pyrmont ; they contain innu- 

 merable remains of encrinites (En. vulgaris and liliformis), 

 and a genus of zoophyte approaching the Isis. 



The multilocular shells of this limestone are principally of 

 the genera ammonites (am. nodosus, capricornus, dorsuosus, 

 amalteus, &c. Schlotheim) and nautilus (N. bidarsatus, 

 Schlot.) Among the bivalves we especially remark the 

 mytili (M. eduliformis, socialis, incertus, costatus), chamae 

 and pectens. The terebratulai (P. fragilis and communis) 

 form true beds in it. The other bivalves of the Linnean 

 genera Mya, Tellina, Donax, Venus, Area, are much more 

 rare. 



Among the univalves, those of the genera buccinum, 

 turbo, and trochus are the most common ; yet these shells 

 occur rather isolated ; and we only here and there observe 

 beds or masses of shells approaching the genus cerithium, as 

 at the Budenberg, near Neustadt, in Hanover, &c. 



Many other genera of univalves are also met with, though 

 rarely, in this deposite ; but it should be remarked that the 

 greater part have only been found near Weymar, Phangel- 

 stad, Tonna, Jena, &c. i. e. in the midst of the great valley 

 situated between the Hartz, the Thuringerwald, and the 

 Erzgehirge. 



It is there that M. Schotheim cites the dentalia (D. 

 loevis and torquatus), the helices of Linnaeus (orientinus,) 

 the neritae (N. spirita and pagana), the patellae (discoidea 

 and mitrata) ; there also are found his lepas avirostris, his 

 solen mytloides, his tellina anseps and minuta, his craniolir 

 tes schroteri, and his curious bitubuUtes irregularis. 



