ACMCEA. 19 



or two crescents, the horns of one directed forward, of the other back- 

 ward. Length 20, breadth 11, alt. 12 mill. 



Sitka south to San Diego, California. 



Patella insessa HINDS, Ann. and Mag. N. H. x, p. 82, t. 6, f. 3. 

 Nacella insessa CPU., Suppl. Rep. Brit. Asso. 1863, p. 650. Acmcea 

 insessa DALL, Amer. Journ. Conch, vi, p. 244, 1. 14, f. 3 (dentition). 



A small, smooth, dark species. Faint, almost obsolete, radiating 

 lines are usually perceptible. It is much larger than A. paleacea 

 or depicta and is not so narrow. Compared with A. asmi it is larg- 

 er, longer, and brown instead of black. 



The Bay of Monterey is probably the central point for this species, 

 in regard to numbers of individuals. It lives on the fronds of sea- 

 weeds. 



A. ASMI Middendorff. PI. 6, figs. 38, 39. 



Shell small, thin but strong and solid, elevated, conical, the base 

 short-oval, apex erect, a little in front of the middle ; slopes of the 

 cone somewhat convex. Surface lusterless, usually corroded, smooth 

 except for very fine radiating stride visible with the aid of a lens, 

 but obsolete in adult shells. Color rusty black. 



Inside black, with a brown zone just outside the muscle-scar. 



Length 10, breadth 82, alt. 7 mill. 



Length 81, breadth 7, alt. 8 mill. 



Sitka to Turtle Bay, Lower California. 



Patella asmi MIDD., Mai. Ross, ii, p. 39, t. 1, f. 5. Acmcea asmi 

 CPR., Amer. Journ. Conch, ii, p. 341. Collisella asmi DALL, I. c. } 

 vi, p. 252, t. 14,.f. 7 (dentition). 



In the suite of thirty or more of this species before me, no speci- 

 mens show characters which warrant a union with any of the other 

 species. It is an erectly conical, solid little shell, of a more rounded 

 outline than A. insessa, and black instead of corneous in color. It 

 is generally found living on Chlorostoma fanebrale or other black 

 shells. 



A. DEPICTA Hinds. PI. 6, figs. 40, 41. 



Shell small, thin, long and narrow, the sides parallel"; apex at the 

 anterior fourth or third. Surface smooth, shining, having light 

 growth-lines. Very light brown, with narrow dark brown stripes 

 radiating from the apex and from the ridge of the back, where they 

 form a series of v's. 



