312 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
one or two radial threads; intermediate valves with one slit, the jugal tract 
acute, with the pleural tract sculptured with oval punctures between 
oblique, almost obsolete, minute threads; the lateral areas defined by a 
single cord, otherwise similarly sculptured; interior bluish-white, the jugal 
sinus narrow, rounded, the sutural laminae broad, the insertion plates 
smooth; gill rows ambient. Length, 19; width, 11; height, 3 mm. (Dali.) 
Type in United States National Museum, No. 293686. Type locality, 
San Diego, California. 
Range. Known only from type locality. 
Mopalia chacei Berry, 1919 
Lorquinia, January 1919. 
Moderately small, oval, with distinctly arcuate side slopes. Head valve 
with ten clear-cut, heavy, pustulose ribs, their interstices heavily granulose. 
Median valves with strong diagonal and weaker sutural ribs, both pustu¬ 
lose, the lateral areas coarsely granulose between them; central areas on 
each side with 18-20 clear-cut, slightly granulose, longitudinal ribs, gen¬ 
erally straight but on jugum becoming finer and converging in front, 
interstices latticed by a system of numerous very fine transverse riblets. 
Tail-valve small, with depressed mucro and shallow posterior sinus. Color 
of shell dull greenish-brown, more or less mottled with various tones of 
brown or green. Girdle narrow for a Mopalia , bearing a primary sutural 
series of short setae, spinose on the upper margin, and 2 or 3 gradually 
smaller series of similar setae outside of these. (Berry.) 
Type in Berry Collection. Type locality, La Jolla, California. 
Range. Known only from type locality. 
Mopalia goniura Dali, 1919 
Proceedings of the United States National Museum, 55:513. 
Chiton of small size with a high arched back, of a yellowish color 
flecked with scarlet; the girdle red, velvety, with numerous sparsely scat¬ 
tered large brown spines (broken off in the type) chiefly near the inner 
border, and smaller ones scattered near the outer part; gill rows about 
two-thirds the length of the foot; anterior valve with 8 slits, posterior with 
4, intermediate valves with single slits; anterior valve with 10 radii, the 
two marginal wider, otherwise the surface is covered with punctate reticu¬ 
lation; posterior valve small, the mucro at the posterior third, sculpture of 
the posterior tract in radial lines of pustules, the central area has very 
similar ornamentation; the posterior sinus is narrow A-shaped, the apex 
[914] 
