1909.] 



NATURAL SCIENCES OF PHILADELPHIA. 



507 



Cave Creek Canyon, for one-eighth of a mile at the head. 



This is another modification of the levettei stock, differing from 

 heterodonta and varicifera by its wider umbilicus and less closely coiled 

 whorls, from the former by deficient lip teeth, and from the latter by 

 the usual presence of a minute parietal tooth. In genitalia it does not 

 differ from typical levettei. While not conspicuously differentiated, 

 we have thought it well to give the form specific rank. 



Ashmunella levettei heterodonta Pils. Fig. 6. 



Proc. A. N. S. Phila., 1905, 241, pi. 15, figs. 81-91. 

 p. 51. 



Nautilus, XVIII, 



This form has the shape of A. levettei, and typically has a low, 

 straight-topped tooth within the outer lip, a small tubercular tooth 

 at junction of outer and basal margins, and a faint prominence in the 

 position of an inner basal tooth. The parietal tooth is minute or 

 wanting. There are barely over 6 whorls, which therefore are a little 

 wider than in A. levettei. 



We have elsewhere noted the extreme variability of the teeth in 

 heterodonta. They may be much more developed than described above, 

 or so degenerate that only faint traces of teeth are discernible. A 

 form-chain connecting levettei and varicifera exists. Whether hybrid- 

 ism plays a part here remains uncertain. 



Fig. 6. Ashmunella levettei heterodonta. Cotype. 



This form occurs in the heads of Ida and Cave Canyons. In one 

 place heterodonta goes over the divide two or three hundred feet, but in 

 no other case do these species cross to the other side of the range. 

 A. levettei or heterodonta are not found in varicifera territory. There is 

 no mingling of Ashmunellas except large and small forms of levettei. 

 The peculiarities of habit, variation, etc., of the Ashmunellas, Oreo- 

 helices, etc., is worthy of a year's study in the Huachucas. The area 



