AHT. 13 PECULIAE SPIEAL FOSSIL FOKMS MANSFIELD S 



southeast of Monument 19, municipality of Ramos Arizpe, State of 

 Coahuila, ^lexico. Collected by P. D. Krynine." Other smaller 

 specimens from the same locality are like the holotype except that 

 their diameters are proportionately somewhat greater. 



DESCRIPTION OP PLATES 



Plate 1 



Fig. 1. Xenohelix? clarki Mansfield, holotype (XI), p. 1. 

 Figs. 2, 3. {Xenolielix? mexicana Mansfield, holotype (X2), p. 2. 

 Fig. 2, end view. Fig. 3, side view. 



Plate 2 



Figs. 1, 2. Xenohelix? clarki Mansfield, paratype (XI), p. 1. 



Fig. 1, side view. Fig. 2, end view of same specimen. 



II. S. GOVERNMENT PRINTING OFFICE 19S0 



