lOO University of Texas Bulletin 



wall, appears on the flank; such is the case of Gastrioceras russiense 

 Tzwetaev^, but Karpinsky^ has shown that this species has only eight 

 lobes and that it thus belongs to Gastrioceras. 



We shall show that we have a form in our fauna which possibly 

 belongs to Paralegoceras but that as it has not been possible to uncover 

 the internal suture the genus cannot be determined with certainty. 



Paralegoceras incertum nov. sp. 

 PI. V, Fig. 1-13 



Shell subglobose, involute, rounded on the flanks and on the ventral 

 region ; cross-section of the whorl nearly hemispherical, greatest width 

 at the umbilical border, whorl much broader than high. Umbilicus 

 very narrow, apparently deep and with a steep umbilical wall. The 

 umbilical border shows a thickened portion which could almost be 

 considered as a broad, rounded, spiral rib that accompanies the um- 

 bilical shoulder. No constrictions are seen on the cast. The body 

 chamber is unknown. 



The septa are very simple (pi. V, fig. 6, 13). The siphonal lobe is 

 divided in two branches by a median saddle; each of the branches is 

 narrow and pointed. The first lateral lobe is f unnel-shaped and 

 pointed, a little deeper than the branches of the siphonal lobe and 

 much broader than either of them. A second lateral lobe is visible on 

 the flank ; it reaches nearly as far down as the first one, but its umbilical 

 flank is much lower. The median saddle of the siphonal lobe is high 

 and slender, slightly constricted near the middle and notched at the 

 top. The external saddle is high, tongue-like but not very broad. The 

 first lateral saddle is not quite as high as the external saddle, but much 

 broader at the base. A second very low and rounded saddle is visible 

 on the spiral swelling along the umbilical border, so that possibly an 

 auxiliary lobe may exist on the umbilical wall, but this could not be 

 observed. 



On one of the casts traces of radial, wave-like, low ribs can be dis- 

 tinguished. They seem to be strongly curved forward on the ventral 

 region. 



'Marie Tzwetaev, Ceph. d. Calc. Carb. de la Russle Centrale, p. 42, pi. 6, fig. 30-34. 

 ''Karplnsky, Amm. d. Artinsk-Stufe, p. 47, fig. 28-a. 



