ARCESTIDAE Mojsisovics 



POPANOCERATINAE Hyatt 



Agathkeras Gemmellaro 



The genus was created by Gemmellaro in 1887 for discoidal involute 

 shells with rounded ventral portion showing an ornamentation con- 

 sisting of spiral striae, a sutural hne showing externally three con- 

 stricted entire saddles and one broad one near the umbilicus, and a si- 

 phonal lobe divided by a bottle-shaped saddle notched at the top. In 

 addition there are three lateral lobes of spatulate form in the external 

 sutures.^ Later on, Gemmellaro^ was also able to show the outline of 

 the internal lobes. These lobes, according to him, consisted of an 

 antisiphonal lobe; one asymmetrical lateral lobe ending in a sharp 

 point; a high, slender and pointed internal saddle and a first lateral 

 one, very low and very broad. 



Mojsisovics^ and also Karpimsky* had united Adrianifes Gemm. 

 with Agathkeras, but other authors, like Haug,^ J. P. Smith^ and 

 Tchernow'' recognized the validity of the genus Adrianites, the latter 

 one showing that Karpinsky's Agathkeras Stuckenbergi belongs to 

 Adrianites. We shall discuss the difference between the two genera 

 later on in our paragraph on Adrianites. 



Agathkeras has been found in the highest Carboniferous of North 

 America (A. ciscoense Smith) and Russia (A. cfr. uralicum) but it 

 seems to be very rare in those strata. In the Permo-Carboniferous, on 

 the contrary, Agathiceras is exceedingly common. Karpinsky, Kro- 

 tow and Tchernow evidently found quite a number of specimens in the 

 Russian Artinsk. Gemmellaro, who describes three different species, 

 says that A. Suessi is the most common of all the ammonoids of the 

 Sicilian Permo-Carboniferous. Freeh says that A. cfr. Suessi is not 



'Gemmellaro, Calc. c. Fusullna, p. 76, et. seq. 



''Idem, Ibid, App., p. 23, pi. C, fig. 20 (not mentioned in the explanation of the plate). 



•Mojsisovics, Arkt. Trlas-Amm., p. 19. 



'Karpinsky, Amm. d. Artinsk-Stufe, p. 63, 84. 



"Haug, Les Amm. du Perm, et du Trias., p. 394. 



'J. P. Smith, Carb. Amm. of America, p. 130. 



'Tchernow, L'Stage d' Artinsk, p. 288, et. seq. 



