38 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Shell very thin, vitreous, subglobose; base obliquely rounded; vertex 
narrowly truncated, narrowly perforated, the spire nearly concealed. 
Aperture as long as the shell, narrow and supine above, expanded below; 
outer lip produced above the vertex and subangulate, obliquely arcuate 
below; columella flexuous, umbilicus distinct. (Tryon and Pilsbry, Manual 
of Conchology.) 
Type not known to writer. Type locality, Scandinavia. 
Range. Bering Sea and Arctic Ocean; circumboreal (Krause.) 
Genus BROCKTONIA Iredale, 1915 
The shell resembles Cylichna ( Bullinella Newton), but has the spire 
almost concealed. (Dali.) 
Distribution. California. 
Brocktonia polystrigma Dali, 1908 
Proceedings of the United States National Museum, 34:246. 
Shell small, white, barrel-shaped, with the posterior part of the outer 
lip extending slightly beyond the apex of the shell; form much as in 
Haminea solitaria Say; apex sunken, imperforate, the spire concealed; 
outer lip partly membranous and contracting in drying; the shell normally 
covered with a thin periostracum, which in drying splits and contracts; 
sculpture of close numerous, spiral rows of emphatic punctations, cover¬ 
ing the shell; aperture ample; outer lip thin and submembranous, its 
posterior extremity rounded over evenly to the suture, the anterior part 
not expanded; pillar lip thin; arcuate, the margin reflected, forming a 
gutter just outside the margin; body with little callus, only one whorl 
visible. Length of shell, 2.8; max. diameter, 2.2 mm. (young shell). 
(Dali.) 
Type in United States National Museum, No. 110649. Type locality, 
off entrance to San Diego Harbor, in 50 fathoms. 
Range. San Diego, California. 
Genus CYLICHNELLA Gabb, 1872 
Shell subcylindrical, spire sunken; mouth narrow behind, widened or 
advanced columella with two folds. (Gabb.) 
This genus has the external form of Cylichna, but it has two distinct 
folds. The upper one is sharp and prominent like that of Actaeon, while 
the lower is more oblique and winds around the columella more like that 
of Cylichna. (Gabb.) 
Type. Cylichnella bidentatus Orbigny. 
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