162 M. E. Beyrich on the Goniatites 



bonarius, even when the shell is wanting^ are visible like ribs on 

 the casts. This occurs in those individuals which were for- 

 merly found in the mine HofFnung, near Werden, and to which 

 Goldfuss specially gave the name carbonarius. The pyritose 

 ammonites which are found in the state of pebbles in the 

 Ruhr, as well as those of the carboniferous limestone, properly 

 so called, of Vise, are casts upon which the lobes are very 

 well preserved, though nothing of the structure of the shell 

 can be perceived. The lobes of A, sphaericus are distinguished 

 from those of the other Goniatites of the carboniferous strata by 

 the dorsal saddle, which, as well as the two saddles of the mid- 

 dle elevation of the dorsal lobe, are not rounded, but on the 

 contrary angulose. A. sphcericus is not met with among the 

 ammonites found in the aluminous schist near Choquier. 



16. Ammonites Listeri, Mart. PI. I. fig. 13, a, b. 



The dorsal lobe is nearly equal in breadth and depth. The 

 middle elevation attains half the height of the lobe : the two 

 saddles are rounded, as is also the dorsal saddle ; the lateral 

 lobe is nearly as deep as the dorsal lobe ; it has, like the last, 

 its two arms sloping towards the lower part, in the form of a 

 tongue. The back, which is broad and rounded, forms a sharp 

 ridge with the side, which descends rapidly towards the inte- 

 rior, and cuts across the lateral saddle in the middle. This 

 latter is of the same height as the dorsal saddle. The increase 

 in height is 0*72, the increase in breadth 0*62. There are six- 

 teen to eighteen chambers in one whorl. The inner whorls 

 are strictly enveloped, even to the ridge which is between the 

 back and the side, so that the sides form a large and deep in- 

 fundibuliform umbilicus. On the back are large and elevated 

 folds. A. Listeri, as it is figured PI. 1. fig. 13, is met with at 

 Choquier in the aluminous schist supervening on the carbo- 

 niferous limestone; it is found in rounded kidney-shaped 

 masses, inclosed by the aluminous schist, which is almost en- 

 tirely composed of ammonites. I am not at present aware 

 that it has been found in the carboniferous limestone of the 

 Rhine. With' this ammonite the A. Diadema and A, atratus, 

 Goldf., are also found at Choquier. In these the form of the 

 lobes is entirely similar. The peculiar characteristic oi A, 



