Permo-Carboniferous Ammonoids of the Glass Mountains 123 



Adrianites seems to occur first in the Permo-Carboniferous. The 

 oldest species is probably Adrianites Stuckenbergi Karp. from the 

 Artinsk. Agathiceras has been found in the Permo-Carboniferous 

 and in the upper Carboniferous of Russia and America. 



Adrianites marathonensis nov. sp. 

 PI. VI, Fig. 47-56 



Shell subglobose, with rounded flank and somewhat flattened ven- 

 tral part, very involute; whorls numerous and deeply embracing; cross- 

 section almost semi-circular in the younger specimens and a little more 

 sub-trapezoidal in the larger ones. The width of the whorls is much 

 greater than the height, the greatest width lying a little above the um- 

 bilical region. At this place the surface of the flank curves gradually 

 down toward the steep but not very broad umbilical wall. The um- 

 bilicus is narrow and deep. Each whorl shows about three moderately 

 deep constrictions. These are sinuous on the flanks, in the form of an 

 open S, and from the ventral shoulder begin to curve forward, form- 

 ing a convexity on the ventral part. The body chamber is unknown. 



None of the specimens shows a trace of shell material, so that the 

 ornamentation remains entirely unknown. 



The septa do not stand very near together ; the external sutural line 

 is slightly cvtrved between the sipho and the umbilicus. It consists 

 (pi. YI, fig. 52, 53) of seven lobes and six saddles, a seventh saddle 

 existing on the umbilical seam. The siphonal lobe is divided 

 into two branches by a low median saddle. Both branches 

 are exceedingly narrow and asymmetrical, ending in a blunt 

 point; they curve from the top outward and then again inward 

 in their lower part. The first lateral lobe is more than twice as 

 broad as each of the branches of the siphonal lobe. The first 

 and second lateral lobes are very similar in shape, being sym- 

 metrical and a little narrower at the top than in the middle, and ending 

 below in a somewhat rounded point. Both are nearly of the same 

 depth, the second a little shallower than the first; but both are much 

 less deep than the branches of the siphonal lobe. The first auxiliary 

 lobe is a little less symmetrical than the first two laterals and much 

 shallower, but about as broad. The second auxiliary is not quite as 



