58 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



albinos. The true nature of such forms among the Molhisca is 

 not yet well worked out, although in any event they are of con- 

 siderable theoretical interest. Very few races of snails are dis- 

 tinguished by characters of such a nature as to strongly sug- 

 gest their probable origin as sudden breaks or "mutations" of 

 the DeVriesian type in the germ plasm of the ancestral fonn. 

 But from the evidence at hand it appears quite reasonable to 

 believe that the racial features of these two forms can be so 

 regarded. 



'&>' 



Epiphragmophora traskii willetti, new subspecies 

 (Plate 4, figs. 3a-3c) 



Diagnosis: Shell depressed-conic, conspicuously umbilicate, 

 the umbilicus deep, permeable to the apex, and having a diame- 

 ter about one-ninth to one-eighth the greater diameter of the 

 shell. Whorls about 6>4 or a trifle less, convex, the last de- 

 scending somewhat in front. Aperture ample and very 

 oblique (45°). Edges of peristome converging and connected 

 by a very thin, transparent parietal callus. Lip but little thick- 

 ened, everted somewhat throughout, but especially at the pillar 

 where it is sufficiently reflected to indent somewhat the other- 

 wise circular outline of the umbilicus. 



Color varying from near Prout's brown to tawny-olive, be- 

 coming a little paler and yellower in the umbilical region, and 

 with a clear-cut, deep, liver brown band of a width of about 2.2 

 mm. on the shoulder, bordered below by a light yellowish band 

 (near naphthalene yellow of Ridgway) of about equal width 

 and above by a much narrower, slightly less clear-cut band of 

 the same color. 



Periostracum somewhat glossy and with a peculiar sheen. 

 Lines of growth very numerous and quite regular. First half 

 whorl delicately hyaline and nearly smooth except for a few 

 weak incremental waves, with a fine weak papillation sometimes 

 superimposed; next whorl and a half very finely and closely 

 granose or wrinkly granose, with numerous, large, elongate, 

 rather distantly spaced papillae superimposed, the latter ar- 

 ranged fairly definitely in retractively curved, very obliquely 

 slanting series; papillae on later whorls nearly, or quite, obso- 

 lete; spiral sculpture consisting of a weakly developed series of 



