1910.] 



NATURAL SCIENCES OF PHILADELPHIA. 



77 



S. micra occurs associated with Ashmunella lepiderma in the same 

 rock slides. Both are modified in the same manner, the shell differing 

 from allied species in being smaller, thinner, dull, with a greater or 

 less development of cuticular processes. The reduced size compared 

 with the species on the opposite side of the canyon is without much 

 doubt due to the sun-scorched exposure. We have not found that 

 living on igneous rock has any tendency to dwarf Sonorellas, though 

 the tenuity of the shell may fairly be attributed to that influence. 



The animal in alcohol is pale grayish, darker on the back. Sole 

 with the usual pale central area and slightly darker side areas, not 

 defined by lines. 



The genitalia of a drowned specimen in good condition from Station 

 10 is drawn in pi. V, figs. 1, 2. Unfortunately the penis was exserted 

 in all of this lot. Except in being smaller and more slender, the organs 

 resemble closely those of S. virilis. The penis in this figure is shown 

 partially everted, the long papilla (pp.) projecting. In fig. 2 the 

 epiphallus is shown partially uncoiled. The flagellum is well developed 

 for a Sonorella. PI. V, fig. 3, represents the organs of another speci- 

 men, from Station 17, with the penis normally retracted. The end 

 of the penis-papilla is shown in outline 



Measurements in millimeters of the genitalia of two specimens 

 follow : 



Genus OREOHELIX Pilsbry. 



The Chiricahua Mountains harbor two groups of Oreohelix with a 

 well-developed nearly black, green or yellow cuticle, so far unknown 

 elsewhere. In one of these, the barbata group, the shell is bi-convex, 

 with whorls of small calibre, a wide umbilical cavity and numerous 

 spiral wreaths of cuticular fringes. The other, the 0. clappi group, 

 has an orbicular shell usually banded, with large tubular whorls and 

 & smaller, rapidly diminishing umbilicus. In one of the forms both the 

 cuticle and the shell beneath possess well-defined spirals similar to 

 the cuticular fringes of O. barbata; but here the likeness ends. In 

 general appearance these Chiricahuan forms have little resemblance 

 to groups of Oreohelix in the Huachucas or elsewhere. The clappi 



