THE NAUTILUS. 31 



(pi. 1, figs. 3, 3a). These are partly transitional to var. 

 mutator. 



The following two are named as sub-species in order that we 

 may have a convenient means of referring to them. They inter- 

 grade, but their modification has been as great as that usually 

 distinguishing species of Helicidse. 



ASHMUNELLA TETRODON MUTATOR n. SUbsp. PI. 1, figS. 3 to 6. 



In color, shape and sculpture this subspecies is like A. tetrodon. 

 As in that species, the upper lip is well reflected from the inser- 

 tion out; former resting stages are often marked by an opaque 

 light streak on the base. In the typical colony there is no 

 parietal tooth and the lip-teeth are much reduced; there are 

 vestiges of the long tooth within the outer margin, and of the 

 two teeth of the basal margin, but in many individuals of the 

 typical colony these vestiges are exceedingly weak, hardly 

 noticeable. There are about 5 whorls. 



Height 6.25, diam. 14 mm. -\ 



Height 6.9, diam. 13.8 mm. [-Station 60. 



Height 6, diam. 12.5 mm. 3 



Height 7, diam. 14 mm., whorls 5J } Q, ,. g. 



Heights, diam. 15 mm., whorls 5f i 



Locality. Station 80 (1914), in Dry Creek Canyon, Socorro 

 Co., N. M. Also Stations 60, 61, 62, 68, in the same canyon. 

 6,000-7,000 feet elevation. 



This is very abundant in some places, where large series of 

 fresh (< bones " were taken, but living ones were rare. It is one 

 of those lawless species, such as we have described from the 

 Huachucas a species which has been caught in the act of los- 

 ing its teeth. Its affinities are clearly with A. tetrodon of the 

 same canyon, and there seems to be no decided break between 

 the most fully toothed mutator and the tetrodon with smallest 

 teeth. 



The specimen described as type of mutator is from a colony in 

 which no specimens have a parietal tooth. Varying forms from 

 this colony (Station 80) are represented in Fig. 5, all being 

 perfectly adult shells. Similar are those from Stations 61, 62, 68. 



In the lot from Station 60 all the shells are rather distinctly 



