Permo-Carboniferous Ammonoids of the Glass Mountains 205 



The specimen is preserved as a cast but shows a characteristic sculp- 

 ture, which is different on the inner and the outer whorls. On the 

 inner whorls we find on the flank numerous rather thick transversal 

 ribs which commence at the umbilical seam, about forty to the whorl ; 

 these are thinner near the umbilical seam and thicken toward the 

 rounded edge between the flank and the venter, where they disappear 

 suddenly. They are slightly inclined forward. On the venter we 

 find extremely fine transversal ribs or lines, nearly invisible to the 

 naked eye, which are strongly curved forward and separated by very 

 fine depressions ; their number is at least twice or three times as high 

 as the ribs on the flanks. On the whorls of medium size, the ribs on 

 the flanks begin to disappear, becoming shorter as well as thinner. 

 They bifurcate toward the venter, which thus shows a much greater 

 number of fine rounded transversal ribs not curved forward, but 

 straight and separated by shallow furrows with rounded bottom, al- 

 most as wide as the ribs. The ornamentation of the largest whorl 

 could not be observed ; it appears to be smooth, but that is frequently 

 the case in casts of Gastrioceras, even where the shell shows strong 

 spiral ornamentations. In our case no spiral sculpture could be ob- 

 served on any of the whorls, although such are nearly always present 

 on Permo-carboniferous Gastrioceras ; but they may possibly have 

 existed on the shell of our specimjens. 



The septa are rather distant from each other on medium-sized 

 whorls, while on the smaller ones they are much nearer together, the 

 flanks of the saddles touching the base of those of the next younger 

 line. The mature suture is very simple. It consists between the sipho 

 and the umbilical seam of three lobes and two saddles. 



The siphonal lobe is very wide and is divided into two branches 

 by a stout and not very high median saddle. This saddle is not more 

 than half as high as the external saddle, broad at the base and slightly 

 tapering toward the upper end. Each of the branches of the siphonal 

 lobe is tongue-shaped, and ends in a sharp point. The first lateral 

 lobe is a Httle less deep than the branches of the siphonal one and a 

 Httle broader than either of them ; it is tongue-shaped ending in a sharp 

 point. The second lateral lobe is much shallower and a little narrower 

 than the first one, but similar in form, terminating also in a sharp 

 point. 



