Permo-Carhoniferous Ammonoids of the Glass Mountains 105 



and two saddles. The second lateral lobe may perhaps exist on the 

 umbilical wall, but could not be observed. 



The siphonal lobe is extremely broad. A median saddle divides it 

 in two branches which are broad, wider above than below, with a bot- 

 tom that has the general outline of a half circle, but which is serrated 

 by seven teeth, the size of which increases from the upper side of the 

 lobe toward the bottom. The first lateral lobe is narrower but about 

 as deep as the siphonal lobe, though less symmetrical ; its deepest part 

 on which the longest tooth shows, lies nearer to the umbilical side, and 

 there are more teeth on the ventral side than on that near the umbilicus, 

 while in the branches of the siphonal lobe the longest tooth is about 

 in the middle of the bottom and the number of teeth is more or less 

 the same on both sides. No second lobe appears on the flank, but it 

 may exist on the umbilical wall, which is covered. 



The median saddle in the siphonal lobe is high, not very broad, 

 slightly notched at the top, a little broader at the base than at the 

 upper end. The external saddle is narrow, higher than the median 

 saddle of the siphonal lobe, and rounded at the upper end. The first 

 lateral saddle is much lower than the external, but broader; it is 

 rounded from the base up to the top, and its outer flank disappears in 

 the umbilical region. 



Dimensions: 



Diameter i7.5 mm • (1) 



Width 23.7 0.50 



Height of the last whorl 28.7 0.60 



Diameter of umbilicus Umbilicus practically closed 



Relation to other species: 



The only species which seems to be nearer related to ours is Thalas- 

 soceras Gemnvellaroi Karp.-^ The external shape is very similar to that 

 of Proth. Welleri, if we take into account that it is a very small speci- 

 men. The ratio of diameter, width and height of the last whorl is 

 I :o.55 :o.55, but it is extremely probable that larger specimens will 

 have whorls that are higher than broad. The suture is very similar 

 to that of our species in its general outline, although there are dififer- 

 ences in the details. For example: the first lateral saddle is much 

 broader in the Russian species, the teeth in the lobes are comparatively 



'Karpinsky, Amm. d. Artinsk-Stufe, p. 80, pi. 4, fig. 3, a-d. 



