222 University of Texas Bulletin 



semilunar cross-section. The umbilicus is very narrow; the wall can not 

 be seen. The flanks are slightly convex, the venter is rounded. The orna- 

 mentation consists of low, rounded, broad, numerous ribs (about 32 to the 

 whorl) which apparently do not reach down to the umbilical region and 

 which are strongest on the ventral portion. On the internal whorl we note 

 a well defined and rather broad constriction which toward the front is 

 limited by a slight thickening ; the constriction is especially evident on the 

 venter. The ribs are curved forwards, as is the case with the constriction, 

 although in less degree. 



Figure 5. Suture, Neoptychites aff. cephalotus Courtiller 



The suture is very similar to that of Neoptychites and corresponds in 

 general to that of Neopychites cephalotus, although the figure published by 

 Pervinquiere is taken from a much larger specimen ; a little more similar 

 still is the suture of the small specimen of N. xetriformis, in the above cited 

 work of Pervinquiere (p. 398, fig. 153) , although there the external saddle 

 is more slender than in our specimen. The suture of our individual is not 

 complete and in some places can not be very well followed, but in general 

 narrow, ending in two branches; the external saddle is quite broad and 

 one recognizes the main features. The external lobe is deep and relatively 

 high and little ramified ; the first lateral lobe is a little shallower than the 

 external one, ends in two points and shows also a branch directed obliquely 

 toward the ventral region ; the first lateral saddle is similar to the external 

 one but is lower and narrower. 



Figure 6. Suture, Neoptychites aff. cephalotus Courtiller 



Dimensions : 



Diameter ............................................. ...... 50mm. (1) 



Height of the last whorl ............................ ^ ........ 2<5 mm. 0.52 



Width of the last whorl ...... .......................... " . . ...... 33 mm. 0.66 



Our specimen represents the juvenile stage of a Neoptychites similar to 

 the one figured by Pervinquiere in pi. 27 fig. 2, which it resembles much in 

 its external features ; it differs mainly in its great width. But according to 

 Pervinquiere the dimensions change much in the genus, and we should not 

 give too much importance to this feature. A specific determination of our 



