A New Ammonite Fauna of the Lower Turanian of Mexico 221 



Pervinquiere 1 more than it does the type. From both species it differs 

 through the absence of an intermediate row of nodules and consequently 

 through the different cross section of tne whorl. From Vascoceras subcon- 

 ciliatum our species is also distinguished by its very reduced and simple 

 suture. In this case it resembles much more Vascoceras polymorphum 

 Pervinquiere, which shows a very similar suture. 



Pervinquiere has extensively discussed the relations of Vascoceras poty- 

 morphum with the other Vascoceras, as well as with Mammites and Acon- 

 thoceras, indicating the similarity of certain groups of Aconthoceras and 

 Mammites, and emphasizing the singular nature of the suture, which is 

 similar to that of other Vascoceras. I believe that Pervinquiere's reasons 

 are well founded and that the present group should be placed in the genus 

 Vascoceras, especially as this genus is nearly related to Acanthoceras and 

 Mammites; therefore the similarity between certain groups of the three 

 genera is not very surprising. 



Vascoceras polymorphum Pervinquiere occurs in the lower Turonian of 

 Tunis; Vascoceras subconciliatum Choffat is found in beds of a similar 

 age in Portugal. Pervinquiere also emphasizes the similarity between this 

 group and a cephalopod from Brazil, Ammonites offaccinatus White, 2 but 

 this latter species is too little known to allow a detailed comparison. The 

 suture is not figured but according to White it is rather complicated. It 

 is therefore possible that it belongs to a different group, or even to a dif- 

 ferent genus. 



Number of specimens : 1. 



Age: Lower Turonian (Salmurian), lower horizon. 



NEOPTYCHITES Kossmat 



NEOPTYCHITES aff. CEPHALOTUS Courtiller 

 PI. 18, figs. 3, 10, 13 



1907: Neoptychites cephalotus Courtiller Pervinqutere, Paleontologie Tunisienne, p. 393, 

 pi. 27, figs. 1-3. Cum syn. 







Among our material exists a cephalopod of small size which in its ex- 

 ternal form and its suture resembles the juvenile specimens of Neoptychi- 

 tes. Its features are : 



Shell subglobose, very involute, last whorl broader than high with nearly 



Pervinquiere, Paleontologie Tunisienne, p. 336, pi. 21, figs. 2-5. 

 'White, Brazil, p. 219, pi. 23, figs. 3, 4. 



