460 Notices of Memoirs— Dr. E. von Mbjsisovics — 



in some cases nothing but the decomposed limestone rock in 

 place, or rather the intercalated impure limestone layers reduced 

 to clay. In other cases the clay has been brought from the 

 neighbourhood into the pot with, or without, lignite. In all cases 

 it is rudely stratified ; some of the layers being full of shot ore and 

 ball ore ; others being nearly pure white, yellow, or black clay. 

 Usually the quantity of ore increases with the depth ; solid floors of 

 ore occur ; or the bottom of the pot is filled with solid ore. 



Up through this ore-bearing clay-mass rise steeples of pipe ore, 

 the tops of which are struck by the miners at various distances 

 beneath the sod. Some of them projected from the forest-covered 

 soil, as humps of pipe-ore, and led to the discovery of the mine ; 

 others were not encountered until the quarry floor had been sunk 

 10, 20, or 50 feet. But in all cases the pipe-ore mass is a steeple, 

 enlarging downwards with ever-broadening base, and standing 

 finally on the limestone foundation at the bottom of the clay. Often- 

 times several steeples unite their bases, like a clump of trees. Some 

 of them have been 100 feet high, and proportionately wide at the 

 base. 



The common idea has been that they are concretionary masses, 

 derived from the moist iron-bearing clays. 



I have long held that all these limonite deposits have been made 

 in caverns. I now suggest that the broader caverns had their roofs 

 supported (for a time) by masses of stalactite (now removed by 

 erosion) and stalagmite ; and that the stalagmite piers have been 

 metasomatized into pipe ore, and remain standing in the surrounding 

 clay. 



1008, Clinton-street, Philadelphia, 

 July 29, 1878. 



itotices oif iMiiEnviioiiRS- 



Ammonites of the Mediterranean and Juvavian Trias. By 



Dr. Ed. von Mojsisovics. 



[Proceed. Imper. Geol. Instit. Vienna, April 1, 1879.] 



(Communicated by Count Marschall, F.C.G.S., etc., etc.) 



General Considerations. 

 niHE forms united in one genus must agree in their least variable 

 a characters (disposition and form of the lobes, form and structure 

 of the shell, length of the body-chamber, and form of the margin of 

 the aperture). In continuous genetic series, the limits between the 

 primary genus and those descending (?) from it must necessarily be 

 traced somewhat arbitrarily. Forms or groups of forms, of sporadic 

 occurrence, not possessing indubitable characters of known genera, 

 are generally best considered as constituting independent genera. 

 Isolated forms, notably aberrant in one direction from the generic 

 type, are provisionally ranked among the primary genera. 



Aroestid^;. 

 The genera Cladiscites, Joannites, and Spliingites being eliminated, 



