310 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
two similar but smaller series interposed in alternation. Median valves 
with lateral areas bounded by rib-like diagonal and sutural series of coarse 
pustules, and with some 2-5 minor series of pustules interpolated between. 
Central areas on each side with 10-14 sharp, flexuose, longitudinal ribs, 
the outer ribs more or less broken posteriorly, the breaks forming radial 
series of granules in front of the diagonal rib. Tail valve with mucro 
strongly posterior, little elevated; caudal sinus strong. Slit formula 8, 1—1, 
1-1. Girdle narrow, armed above with a microscopic spinulation, and 
both major sutural and several minor series of beard-like setae. Color 
brownish-cream, with yellowish-brown mottlings. (Berry.) 
Type in Berry Collection. Type locality, off Point Pinos, California. 
Range. Known only from type locality. 
Mopalia lowei Pilsbry, 1918 
Nautilus, 31:125. 
The Chiton is rather small, oblong, moderately elevated, carinate, the 
lateral slopes straight. The valves are irregularly mottled with ferruginous, 
sea-green, and olive. The anterior valve has ten radial ribs, those at the 
suture bearing compressed tubercles, the others rounded tubercles. The 
intervals are also tuberculose, with some interstitial granulation. Valves ii 
to vii have low, tuberculose sutural and diagonal ribs, the lateral areas 
tuberculose and granular. Central areas with the jugal tract closely striate 
longitudinally, the striae converging forward near the beaks, elsewhere 
subparallel, but slightly irregular in places. Pleural tracts having longi¬ 
tudinal ribs, near the ridges converging forward somewhat, becoming 
divergent toward the lateral borders. These are intersected by a system 
of much weaker curved ribs radiating forward and laterally, forming 
oblong tubercles on the longitudinal ribs. The posterior valve is short, 
nearly flat, with a broad, shallow posterior sinus, the scarcely raised mucro 
being at the posterior third. The interior is nearly white, strongly striate 
across the central part, where some valves may show a green or pink stain. 
The posterior valve has a rather deep posterior sinus and a single slit on 
each side. The girdle is rather narrow in dry specimens, and bears coarse 
processes covered with sharp spines. Length, 23; width, 12.2 mm. 
(Pilsbry.) 
Type in Philadelphia Academy of Natural Sciences, No. 117951. Type 
locality, San Pedro, California. 
Range. Known only from the type locality. 
