CLASS GASTROPODA 
265 
total length of the animal is about the same in the two species. The eleva¬ 
tion is about equal also, but in californica the girdle is generally wider at 
the sides, especially in old specimens. In size, individuals of the northern 
species considerably exceed any of the southern I have seen, although the 
majority of specimens do not differ much. (Tryon and Pilsbry, Manual of 
Conchology.) 
Type in United States National Museum? Type locality ? 
Range. Point Conception, California, to Gulf of California. 
Nuttallina thomasi Pilsbry, 1898 
Proceedings, Philadelphia Academy of Natural Sciences, 289:1898. 
General form oblong, rather depressed, not keeled dorsally; surface 
granulose when not eroded. Color blackish or dark brown, with a whitish 
band on each side of the median line of back or irregular whitish macula- 
tions; girdle dark. Intermediate valves short and wide, with a slight or 
hardly noticeable depression on each side of the jugum, and others in 
front of and behind the scarcely defined, obsolete, diagonal convexity, the 
anterior and posterior margins subparallel, slightly arcuate. Anterior valve 
granulate, without radial ribs, the posterior margin excavated mesially. 
Posterior valve with tegmentum slightly wider than the anterior, the obtuse 
mucro somewhat behind the middle. Interior blue-green, with the area 
behind the valve-callus dark brown, or livid purplish, with the light sutural 
laminae and blue-green area behind the sinus. Length, 15; breadth, 8 mm. 
or smaller. (Pilsbry.) 
Type in Philadelphia Academy of Natural Sciences. Type locality, 
Monterey, California. 
Range. Known only from type locality. 
Genus SCHIZOPLAX Dali, 1878 
Shell and zone like Tonicella; central valves with a median slit. Bran¬ 
chiae subambient. (Tryon, Structural and Systematic Conchology.) 
Type. Chiton Brandtii Middendorff. 
Distribution. Arctic to Sitka, Alaska. 
Schizoplax multicolor Dali, 1920 
Nautilus, 34:22. 
Chiton depressed, broad, wider behind than in front, maroon varied 
with white streaks, with a rather wide girdle, the surface of which is 
covered with soft bristles like those of Mopalia muscosa, among which 
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