210 University of Texas Bulletin 



rounded, nearly straight ribs which sometimes are scarcely perceptible; 

 on the last whorl we count thirteen of these ribs. The ribs begin on the 

 umbilical border in a strong and pointed nodule and end with another 

 and still more prominent but somewhat longitudinally elongated nodule 

 on the ventral shoulder. Between the two rows on the ventral shoulders 

 we observe a smooth and very slightly convex zone which does not show 

 any signs of nodules or ribs ; only the two last nodules seem to be connected 

 by a kind of low rounded rib which crosses the smooth zone of the venter. 

 Between the nodules of the rows on the ventral shoulder we find some 

 ribs or nodules intercalated which do not correspond to umbilical nodules. 



Traces of the suture are visible in different parts but I have not been 

 able to draw a complete line. 



Dimensions : 



Diameter: 214 mm. 



The last part of our specimen bemg somewhat crushed and twisted, we 

 have taken the following dimensions frcm a little smaller diameter : 



Diameter 164mm. (1) 



Height of the last whorl 63 mm. 0.38 



Width of the last whorl 70 mm. 0.43 



Diameter of the umbilicus 59 mm. 0.36 



Height of the last whorl on the same diameter but half a whorl back- 

 wards 42 mm. 0.26 



Width of the last whorl on the same point 45 mm. 0.27 



Our specimen belongs, as we have already mentioned, to the group of 

 Pseudaspidoceras Footeanum Stoliczka 1 which it resembles in its involu- 

 tion, the cross-section of the whorls, the two series of prominent nodules, 

 etc. It differs from the type through its weaker ribs, and the entire ab- 

 sence of ribs and nodules on the ventral portion and of a concave zone 

 along the line of symmetry on the ventral portion. 



Our species shows much nearer relations to Pseudaspidoceras pedroanum 

 White from Brazil than to the type of the group. It has the same kind of 

 involution, a very similar cross-section, a nearly identical ornamentation; 

 it only seems to differ a little with respect to the nodules on the ventral 

 shoulder, which according to the figure of White are connected on the 

 last part of the whorl by a kind of low crest, which is also mentioned in 

 the text. White also says that in very large individuals the nodules on 

 both sides of the venter are connected by a crest which crosses the venter. 

 We have indicated a similar phenomenon in the last two nodules of our 

 specimen. We thus see that our species resembles in a surprising man- 

 ner Ammonites pedroanus Kossmat and others have already recognized 



