Permo-Carhoniferous Ammonoids of the Glass Mountains 147 



we tried to show that in our lowest Permo-Carboniferous, and possibly 

 in the Pennsylvanian, there are certain species which show the general 

 form of the saddles and lobes of Stacheoceras but which distinguish 

 themselves by a much smaller number of lobes on the external side, 

 and which have very characteristic internal lobes that are entirely 

 different from those of the typical Stacheoceras. In our material 

 there are two more species, the septa of which show a marked dif- 

 ference from those of Marathonites. The differences are so great 

 that I propose a subgeneric name for this group, which is easily dis- 

 tinguishable from Marathonites, even where the form of the internal 

 sutures cannot be ascertained. 



The new subgenus Vidrioceras shows the following features : 

 Shell of rather globose form, flattened on the flanks of the inner 

 whorls, but rounded on the outer ones ; cross-section rather trapezoidal 

 in youth, semilunar in an advanced stage; very involute in the adult 

 stage while younger specimens .are much less so; umbilicus wide in the 

 inner whorls and narrow in the outer ones. Whorls deeply em- 

 bracing and very slowly growing. Surface ornamentation composed of 

 faint transversal undulations decidedly curved toward the front. Each 

 whorl shows on the cast two to three deep constrictions equally curved 

 toward the front. 



The suture (pi. VII, fig. 60, 61 ) consists of nine lobes and ten saddles 

 on the external part between the two umbilical shoulders; of two 

 lobes and one saddle on each side of the umbilical wall (together, four 

 lobes and two saddles) ; of seven lobes and eight saddles on the niter- 

 nal side. The whole suture line is therefore composed of twenty lobes 

 and twenty saddles. All the saddles are entire, rounded at the top, and 

 the first three lateral saddles of the external side as well as those on the 

 internal side, are slightly constricted. The siphonal lobe is divided in 

 two branches by a high median saddle; the first lateral lobe is bifid, 

 the second ends in one point; the first auxiliary is again bifid in the 

 type species, while in the other species the second lateral and the first 

 auxiliary lobes develop each a small secondary point. The antisiphonal 

 lobe is divided in three branches by two relatively high and slender 

 saddles, the middle branch being much deeper than the lateral ones. 

 The internal first lateral lobe is bifid, the second is symmetrical, and 

 ends in one point, while the first auxiliary does the same, but is asym- 



