512 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.55. 



uniform over the surface; anterior valve with 11 subcarinate radial 

 ribs, the two posterior tending to bifurcate, and nine slits; the ribs 

 are hardly nodulous, and in the type the interspaces are reticulated 

 only on the left side of the axis; posterior valve with 13 slits, nine 

 nodulous riblets, the mucro subcentral, the central area axially 

 threaded with a median smooth keel; intermediate valves with a 

 smooth narrow keel at the jugum, the pleural tracts with a strong 

 rectangular reticulation; the lateral areas with two strong keeled ribs, 

 the posterior rib bifurcate for most of its length and the distal ends 

 sometimes divided; these ribs are more or less nodulous, denticulat- 

 ing the posterior edge of the valve; the interspace between the main 

 ribs is deep and angular ; the insertion plates have a single slit ; the 

 interior of the posterior valve in dark green, of the other valves 

 greenish white; the jugal sinus is very shallow, straight edged and 

 wide, the sutural laminae rather narrow. Length, 21.5; width, 10; 

 height, 5 mm. 



IlahitaL— San Pedro, California. Cat. No. 109488, U.S.N.M. 



This is another species which verges toward Ischnochiton. 



CALLISTOCHITON FISHERI, new species. 



Chiton light greenish gray, small, strongly sculptured, the girdle 

 covered with minute closely crowded gray scales giving a velvety 

 aspect; anterior valve with 12 strong annulate radial ribs with 

 narrower interspaces, internally with 11 slits; posterior valve with 

 the mucro behind the center, the central area coarselj?^ irregularly 

 reticulate, the posterior area elevated, with six strong annulate ribs, a 

 slit to each rib, a roundly excavated jugal sinus and narrow rec- 

 tangular sutm-al laminae; the interior is dark green; intermediate 

 valves with one feeble slit at each end, excavate rather than mucro- 

 nate at the jugal area which is obliquely reticulate, passing into the 

 pleural tracts which are small, axially threaded, the interstices with 

 minute transverse threads; lateral areas with two annulate ribs, 

 the posterior stronger, denticulating the posterior edge of the valve; 

 internally pale greenish with a wide shallow straight edged jugal 

 sinus and narrow sutural laminae. Length, 10; width, 5; height, 3 

 mm. 



Hahitat. — Glory of Russia Bay, Tanaga Island, Aleutians, on a 

 sponge thrown up by the surf; W. J. Fisher. Cat. No. 110353, 

 U.S.N.M. 



CALLISTOCHITON DUNCANUS, new species. 



Chiton small, yellowish white, strongly sculptured, with a velvety 

 girdle densely covered with minute whitish spinules, fringed a little 

 at the outer margin; anterior valve with nine strong annulate ribs 

 with subequal interspaces and seven slits; posterior valve with sub- 

 central mucro, the central area axially threaded, the posterior tract 



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