Permo-Carhoniferous Ammonoids of the Glass Mountains T15 



frequently visible also on the casts but generally they disappear with 

 the shell material so that the casts become entirely smooth. 



The septa are widely separated from each other even in the inner- 

 most whorls. The suture (pi. V, fig. 42, 47; pi. VI, fig. 2) forms a 

 straight line from one umbilicus to the other. The external suture 

 consists of a siphonal lobe divided by a median saddle ; of three lateral 

 and auxiliary lobes on each side, connected by three saddles ; and of a 

 fourth one in the umbilical region. Each branch of the siphonal lobe 

 is a little broader than the first lateral lobe. These branches, as well 

 'as the three lateral lobes, are all of the same form — pointed below, 

 widest below the middle, and narrower at the upper end. They de- 

 crease in width and depth from the first lateral to the first auxiliary. 

 The siphonal saddle is high 'and slender, well constricted in the middle 

 and notched at the top. The external and the first lateral saddle are 

 similar in outline but the first lateral one is lower and narrower than 

 the external; both are nearly symmetrical, entire, rounded at the top 

 and constricted in the middle. The second lateral saddle is a little 

 asymmetrical, showing a deeper constriction on the inner side. It is 

 narrower and lower than the two preceding ones. The first auxiliary 

 saddle is a little lower than the second lateral, but very broad and asym- 

 metrical, the inside flank being much steeper than the outer one. 



The internal sutures (pi. VI, fig. 3) are very simple; they consist 

 of a narrow antisiphonal lobe, of triangular form, ending in one single 

 point, and of one lateral lobe, similar in form to the antisiphonal but 

 asymmetrical. These lobes are connected by a tongue-shaped, high 

 internal saddle, and a broad and low first lateral saddle, which unites 

 on the umbilical seam with the first external auxiliary saddle by means 

 of a wide and rather shallow lobe. 



The suture corresponds in every detail to that of the type of the 

 genus, Agathiceras Suessi, as it was figured by Gemmellaro.^ 



The character of the septa is very constant in our species, even as 

 small a specimen as No. XIII of our dimension table having exactly 

 the same external suture as the largest one. 



'Gemmellaro, Calc. c. Fusulina, app., pi. C, flg. 20. 



