PACIFIC COAST SPECIES. 131 



by distinctly characterized varieties. Many of tliese were desciibed as 

 distinct species, and justly so, as tbey were so different from tlie forms 

 before known, and the many connecting links of variation were at the 

 time undiscovered. It is now safe, however, to declaie that .4. Cali- 

 forniensis, ranging as a coast species from Mendocino County to Mon- 

 terey, comprises many forms, variable as to shape from extremely glo- 

 bose to depressed, in the umbilicus being widely open or entirely closed, 

 in the thickness of the shell, and its size. Several prominent forms 

 are mentioned below as varieties, their synonymy being given sepa- 

 rately. All these forms agree in having the i^eculiar reticulated or 

 granulated surface. This is noticed in no other species, except slightly 

 on the upper whorls of A. arrosa. 



Jaw of the typical Californiensis arcuate, of uniform width through- 

 out ; ends blunt ; anterior surface with 4-5 distant, stout ribs, creuu- 

 lating either margin. 



One lingual membrane had 176 rows of 56-1-56 teeth each. An- 

 other membrane (Terr. Moll., V, Plate IX, Fig. S) had 53-1-53 teeth. 

 All the teeth are as usual in the genus. The central and first laterals 

 have no distinct side cusps or cutting jioints, though the latter are rep- 

 resented by lateral bulgings on the large cutting i)oint. The side cut- 

 ting points and cusps are distinctly developed on the ninth tooth. 

 There are about 24 laterals, the inner cutting point of the twenty-fifth 

 tooth being bifid. The thirty-ninth and fifty-third (and last) teeth, 

 shown in the plate, are true marginals. 



The genitalia are as described below in var. Nlcldiniana. 



Var. Nickliiiiana, Lea. 

 Shell subumbilicated, conic-globose, rather thin, the surface lightly 

 marked by the lines of growth, faintly indented and delicately sha- 

 greeued with fine microscopic granules arranged in fio. los. 



quincunx ; pale horn-color or sometimes cinereous, 

 girdled with a single narrow chestnut bronze zone, 

 paler at its edges; the whole covered with a thin, 

 yellowish brown epidermis; spire elevated ; whorls C, 

 moderately convex, the outer one ventricose, with a. xicidijiUma. 

 some approach to an angular periphery; base tumid, depressed at 

 center and perforated by a very small umbilicus; aperture rounded, 

 forming two-thirds of a circle, banded within ; peristome white, slightly 

 reflected above, more so below, until at the umbilicus it is quite revo- 

 lute and mostly covers the opening. Greater diameter 28, lesser 23""™; 

 height, 19"'"'. 



