278 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Genus METAXIA Monterosato, 1884 
Base truncate, basal area not cingulate and concave, canal open, incip¬ 
ient. (Tryon, Manual of Conchology .) 
Type. Ceritkiopsis rugulosa Sowerby. 
Distribution. California, Italy, Mediterranean. 
Metaxia diadema Bartsch, 1907 
Proceedings of the United States National Museum , 33:182. 
Shell slender, decidedly turreted, brown. Nuclear whorls four, the first 
smooth, the others marked by two spiral threads, the posterior one of 
which falls on the middle of the whorls between the sutures, while the 
anterior one is about halfway between it and the basal suture. In addition 
to this sculpture there are slender, equal, and equally spaced, axial riblets, 
of which about 28 occur upon the third and 30 upon the fourth whorl. 
The nuclear whorls are slopingly shouldered from the posterior keel to the 
summit and well-rounded anterior to it. The demarcation between the 
sculpture of the nuclear turns and the post-nuclear turns is abrupt. Post- 
nuclear turns inflated, marked by four, strong, spiral, tuberculate keels and 
axial ribs. These four keels are equally spaced, but not equally strong. 
The third excels all the others in development, the fourth or basal one 
comes next, the second next, while the one at the summit is the weakest 
of the four. The axial ribs are broad and strong and rather distantly 
spaced, forming decided nodes at their intersection with the spiral keels. 
There are about 14 of these ribs upon the first, 15 upon the fifth, and 22 
upon the penultimate turn. The spiral keels connecting the tubercles are 
only about one-fourth as strong as the axial ribs; the areas inclosed by the 
two are quadrangular, the vertical diameter being the shorter. On the last 
whorl, where the ribs are a little more crowded, these areas become 
squarish. Sutures strongly constricted. Periphery of the last whorl marked 
by a strong keel, separated from the supraperipheral keel by a strong 
channel, which is crossed by the continuations of the axial ribs. Base 
rather short, sloping somewhat concavely from the peripheral keel to the 
insertion of the broad columella, marked by a weak spiral thread at the 
base of the columella and the continuation of the axial ribs, which extend 
well up on the columella. Aperture suboval, decidedly channeled at the 
junction of the lip and columella, with the posterior angle obtuse. Length, 
3.8; diameter, 1.3 mm. (Bartsch.) 
Cotypes in United States National Museum, No. 195203. Type local¬ 
ity, San Pedro, California. 
Range. Monterey to off Point Loma, California. 
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