224 University of Texas Bulletin 



lateral saddle is narrow, a little lower than the external saddle, and little 

 ramified ; second lateral lobe is similar to the first in its form but smaller 

 and much shallower ; the second lateral saddle is very low and very broad 

 and of oblique form. 



Dimensions : 



Diameter 73 mm. (1) 



Height of the last whorl 40 mm. 0.55 



Width of the last whorl 33 mm. 0.45 



Diameter of the umbilicus 6.5 mm. 0.09 



With respect to its external form our specimen is very similar to Neop- 

 tychites xetriformis; even the dimensions coincide sufficiently, if we take 

 into consideration the variability of Neoptychites. The main difference 

 consists in the ornamentation; the ribs are much more numerous in our 

 species (probably 25 to 30 on the last whorl) and they do not disappear 

 completely on the venter. The specimen thus occupies an intermediate 

 position between N. cephalotus and N. xetriformis, or between this and 

 2V. xetra, if the small individual figured by Stoliczka 1 really belongs to N. 

 Xetra. The suture of our specimen resembles that of N. Xetra still more 

 than that of N. xetriformis. 



N. xetriformis occurs in the lower Turonian of Tunis. N. Xetra 

 Stoliczka belongs to the lower and middle Utatur group according to Koss- 

 mat, but we should not forget that the determination of the horizons of 

 the Utatur group is in general based on the petrographical character of 

 the fossils and on the locality. The determination of the age is therefore 

 not always certain for each species. How doubtful it sometimes is we can 

 see in our own case. On page 168 (72) Kossmat cites N. Xetra from the 

 lower and middle Utatur group; on page 196 (131) he cites it from the 

 lower and upper Utatur group. This doubt with respect to the age of the 

 different species can not surprise us. because Kossmat could not base his 

 determinations on well divided and stratigraphically well studied cross 

 sections, but rather on general observations and subdivisions based more 

 on the petrographical character of the rocks than on the faunas. Kossmat 

 himself (loc. cit. p. 132 (197)) is convinced that a paleontological and 

 stratijrraphical subdivision of the Utatur group is possible, but until this 

 has been executed in a modern manner, we should not crive too much im- 

 portance to the age which has been assigned to a certain species from In- 

 dia. We should always take into account that in such old collections labels 



'Stoliczka, Ceph. Cret. Rocks India, pi. 61, fig. 2. 



