248 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
are a little nearer to each other than to the sutures. The anterior one of 
these keels is much more strongly developed on the last nuclear turn than 
the posterior member. The intersections of the spiral keels and axial 
riblets are tuberculate. The whorls have a strong sloping shoulder which 
extends from the posterior keel to the summit. Post-nuclear whorls sepa¬ 
rated by strongly marked sutures, ornamented by two spiral rows of 
nodules, of which the posterior one is the stronger. These two rows 
of nodules are separated on the first seven post-nuclear whorls by a spiral 
channel almost as wide as the suture. From the seventh post-nuclear whorl 
on, a slender, spiral, weakly tuberculate cord makes its appearance in the 
channel, growing stronger with each succeeding turn. This cord is situ¬ 
ated a little nearer the posterior row of tubercles than the anterior, and 
like the posterior row of tubercles is white. The tubercles are connected 
by blunt, ill-defined, axial riblets. There are about twenty tubercles on 
the first and fifth post-nuclear whorls and twenty-four upon the penulti¬ 
mate turn. In addition to the strong sculpture just defined, the entire 
surface, tubercles and depressions, are crossed by many fine lines of growth 
and spiral striations. Periphery of the last whorl marked by a slender, 
weakly tuberculate keel. Base exceedingly short, almost flat, crossed by 
strong lines of growth and fine spiral striations, marked by a brown band 
at the insertion of the columella. Aperture subquadrate, outer lip sinuous, 
conforming with the external sculpture, basal wall slightly concave; colu¬ 
mella very stout, short, and strongly twisted. Basal channel well developed. 
Length, 5.3; diameter, 2.2 mm. (Bartsch.) 
Type in United States National Museum, No. 193998. Type locality, 
Catalina Island, California. 
Range. Catalina Island to Laguna Beach, California. 
Trifora stearnsi Bartsch, 1907 
Plate 71, fig. 3 
Proceedings of the United States National Museum , 33:254; PI. 16, fig. 3. 
Shell elongate-conic, sinistral, flesh colored. (Early whorls decollated.) 
The nine remaining are moderately high, marked by a double spiral row 
of very strong, equally developed, rounded tubercles, which are separated 
on the first three turns by a channel as deep and well-marked as the 
sutures. This space between the two rows of tubercles gradually develops 
into a slender tuberculate keel, which on the last turn is about half as wide 
as the tubercular ridges. There are about eighteen tubercles on the third 
to the seventh of the remaining whorls and twenty on the penultimate. 
Periphery angulated. Base short, marked by two strong spiral keels. 
(Aperture fractured.) Length, 4.1; diameter, 1.4 mm. (Bartsch.) 
[546 ] 
