260 University of California Publications in Zoology  [Vou. 14 
The Farallon Islands is given as the most northern range of this 
species by both Carpenter (1863) and Cooper (1870). It was not 
obtained by the Survey. 
Range.—Crescent City, California, to Gulf of California (Dall). 
Adula H. and A. Adams 
Adula falcata (Gould) 
Lithodomus falcata Gould (1851), p. 87; (1862), p. 213. 
Adula falcata, Carpenter (1863), p. 644; Cooper (1870a), p. 55. 
Description.—The original description is in Latin, a free translation of which 
is given below: 
Shell fragile, subeylindrical, curved, posterior side sloping; umbones strongly 
angulated, pearly; epidermis dull chestnut colored, with occasional bifureate 
wrinkles. Umbones situated in the anterior octant, strongly curved, anterior 
side dilated, subglobose; posterior side curved, compressed, pointed, fringed 
above. 
Both Carpenter (1863) and Cooper (1870) report this rock-boring 
mollusk from this region. Not found among the collections of the 
Survey, although it occurs abundantly along the rocky shores outside 
of the Golden Gate. 
Range—Coos Bay, Oregon, to San Diego, California (Dall). 
Adula stylina Carpenter 
Plate 18, figure 5 
Adula stylina Carpenter (1863), p. 644 (1864b), p. 425. 
Description.—The following is a translation by Professor Clark of Carpenter’s 
Latin description of the species: 
“*Shell cylindrical, lithophagus-like, smooth, very thin, somewhat pointed, 
subnacreous, white, posterior end sometimes tinged with blue; epidermis shin- 
ing, smooth, thick, dark brown; young shells typically modiolaraeform, umbones 
directed anteriorly; anterior dorsal margin slightly crenulated; adult shell with 
dorsal and ventral margins nearly parallel; anterior and posterior margins 
rounded; umbones worn, not conspicuous, situated about one-sixth the distance 
from the anterior to the posterior extremity; incrustation thin, porous, covering 
the posterior area diagonally, prolonged beyond the valves; internal ligament 
prolonged posteriorly; inner surface pale; posterior abductor scar pear-shaped, 
anterior larger, not impressed, oblong; anterior pedal scar large, circular, im- 
pressed; with a subumbonal callosity, conspicuous toward the pedal scar.’’ 
Length, 14 mm. 
Occurrence.—At station D 5809 (7). 
This rock-boring mollusk is represented by a single specimen 
dredged from 53 fathoms in the outer portion of the Golden Gate. 
Range.—Vancouver Island to San Diego, California (Orcutt). 
