1896.J -t)J [Smith. 



lobe by a secondary saddle ; the shell is then in the ephebic or adult 

 stage, and in Pronorites gets no higher in its development. 



The sutures are then constant in shape, and consist of a three-pointed 

 siphonal lobe, a tirst lateral lobe deeply divided by a secondary saddle 

 and five secondary lateral lobes outside the umbilical border, and one 

 on the umbilical shoulder. All the lobes are pointed, and the saddles 

 rounded. The inner lobes, covered by the involution, are unknown. 



The sutures, as figured on PI. xxiv, Fig. 4, show some difterences from 

 those figured by Phillips, PI. xxiii, Fig. 9, and by Karpinsky,* PI. xxiv, 

 Fig. 9/. On the Arkansas specimen the three-pointed siphonal lobe is 

 longer than on the type of Phillips, or the variety P. cyclolobus, variety 

 uralensis Karpinsky, the secondary sinus on the first lateral lobe is deeper, 

 and the second lateral lobe is proportionally longer. In this the Arkan- 

 sas specimen does not depart further from the type than the variety 

 uralensis. But if this difference should be thought to be of sufficient 

 importance to characterize a new variety, the name P. cyclolobus Phil- 

 lips, variety arkansiensis is proposed. 



Surface Markings. — The shell is smooth and devoid of constrictions 

 or other ornamentation, but on the body chamber of the adult, Kar- 

 pinskyf observed weak ribs, that are stronger on the abdomen and grow 

 A\ eaker towards the umbilicus. 



Affinities. — Tliis species is certainly a variety of Pronorites cyclolobus 

 Pliillips ( Geol. Yorkshire, Vol. ii, p. 237, PI. xx, Figs. 40-42), but is more 

 involute at the corresponding diameter, and has a narrower umbilicus 

 and a greater number of lateral lobes. Specimens described by De 

 KoninckJ from Belgium, and by Roemerg from the Hartz mountains in 

 Germany, agree perfectly with the type of Pi'onorites cyclolobus ; the 

 English, Belgian and German beds, in which the species was found, are 

 all older than the Lower Coal Measure horizon in Arkansas in which it 

 was found, and considerably older than the Upper Carboniferous lime- 

 stone, in which it was found in the Ural mountains From this Kar- 

 pinsky || thinks the variety uralensis represents a mutation from the type 

 of the species. 



The form from the Pyrenees described by Barrois^ as Pronorites 

 cyclolobus Phillips has been shown by Karpinsky** to be a new species, 

 P. barroisi Karpinsky. This form is more evolute than even the type 

 of P. cyclolobus, and its lobes and saddles are broader and also less 

 numerous. 



Occurrence. — Pronorites cyclolobus Phillips, variety arkansiensis J. P. 

 Smith, was found with Oastrioceras branneri, sp., nov. J. P. Smith, in 



* Ammoneen der ArUnsk-Stufe, PI. I, Fig. 4 1. 

 t Op. cil., p. 9, PI. I, Fig. 4 c and d. 



I Faune dii Calc. Carbon Belgique, Vol. ii, p. 121, PI. 1, Figs. 5 and 6. 

 ^, Pahtonlngraphica, Vol. ix, p. 167, PI. xxvii, Fig. 1. 



II Ammoneen d. Artinsk-Shi/e, p. 10. 



^ Re.' Ii'i-clie.-; s. I. ten: anc. d'Asturies ei de la Gallce, 1S82, p. 295, PI. xiv, Fig. 2. 

 ♦* L'/c. eil. 



