132 University of Texas Bulletin 



against the next one that, while the outside is completely destroyed, 

 the inner part of the whorl then appears to be the external side of the 

 next one, but shows the internal sutures of the larger whorl. 



We have the same case in the present species (pi. VI, fig. 73). We 

 distinguish an antisiphonal lobe, somev/hat similar to that of Mara- 

 thonites; it is divided into three branches by two relatively long and 

 slender saddles, but while these are nearly parallel in Marathonites, 

 they are strongly inclined toward the middle branch and much shorter 

 in this species. The middle branch is lanceolate, while the side 

 branches seem to be a little asymmetrical and to end in a single point 

 which lies nearer to the inner side. The first lateral lobe is asymmetri- 

 cal and bifid, the outer point being longer than the inner one; the 

 second lateral and the first, second and third auxiliary lobes appear to 

 be all trifid, the middle point being considerably more prominent than 

 either of the two lateral ones. There appears to be a fourth auxiliary 

 lobe on the umbilical seam, but its figure could not be made clear. 

 The lobes decrease in depth from the first lateral to the third auxiliary. 

 The saddles are all very high, slender, entire, rounded at the top and 

 constricted near their base. There are one internal, two lateral and 

 three auxiliary saddles visible, the first one being a little bent over 

 toward the sipho. The saddles decrease gradually in height from the 

 first to the last one. 



The septa are well separated from each other. 



Although the external sutures are not known, there does not exist 

 any doubt that the species belongs to Stacheoceras or a new subgenus 

 of it. The antisiphonal lobe is certainly different from those figured 

 by Gemmellaro (loc. cit., app., pi. C, fig. 6, 8) but we shall see that 

 in Marathonites exists a similar one. For the moment being, we 

 have to leave our species with Stacheoceras on account of our im- 

 perfect knowledge of the suture, but we may already state that the 

 species belongs either to Marathonites or more probably to another 

 subgenus, with a greater number of lobes and a somewhat different 

 antisiphonal lobe. 



Dimensions : 



Diameter 10.2 mm (1) 



Width 10.1 0.99 



Height of last whorl 4.5 0.44 



Diameter of umbilicus 1.1 0.11 



