510 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.55. 



slits, posterior with 2 slits, intermediate valves with single slits; 

 anterior valve with about 10 feeble radii, otherwise minutely punc- 

 tate-reticulate ; posterior valve small, with subcentral mucro and 

 similar sculpture; intermediate valves with the jugal and pleural 

 tracts not separated, mucronate, sculptured with obliquel}' axial very 

 fine threads with punctate interspaces; the lateral areas bounded by 

 a slender, sometimes beaded rib in front and a marginal thickening 

 behind, otherwise sculptured like the rest of the valve; internally 

 whitish with a wide and shallow jugal sinus and prominent sutural 

 laminae. Length, 8 ; width, 4.5 ; height, 2 mm. 



IlabitaL—CatQlmii Harbor, California, W. H. Dall. Cat. No. 

 172900, U.S.N.M. 



CALLISTOCHITON ACINATUS, new species. 



Chiton small, yellowish white, strongly sculptured; the anterior 

 valve with nine nodulous ribs with narrower interspaces, a minutely 

 granulose surface and about 12 inconspicuous slits; posterior valve 

 with 18 slits and 6 nodular ribs ; this valve is much smaller, the cen- 

 tral tract is narrow and coarsely reticulate ; intermediate valves some- 

 what mucronate ivith 1 slit at each end ; the sculpture on the lateral 

 areas consists distally of two very prominently pustulate ribs, toward 

 the dorsal ridge there are only crowded minor pustules; the jugal 

 and pleural tracts are coarsely reticulate, the interspaces deep; the 

 girdle yellowish with densely crowded microscopic imbricating scales ; 

 length, 6; breadth, 3; height, 1.5 mm. 



Habitat. — Shore at San Pedro, California. Cat. No. 218773, 

 U.S.N.M. 



Though very minute, this does not seem to fit in with the adult of 

 any of the other species. 



CALLISTOCHITON CELETUS, new specieg. 



Chiton of moderate size, pale brownish, with a mottled white and 

 brownish girdle scaled like the preceding species ; anterior valve with 

 11 nodulous ribs, which, except the closer set posterior pairs, have 

 about equal interspaces; this valve has 9 slits, each corresponding 

 to a rib, the posterior valve has 24, but only 6 ribs which are mostly 

 split for a short distance distally ; this valve is conspicuously convex, 

 with about. 6 large smooth nodules to each rib, the central tract is 

 narrow and coarsely axially threaded ; in the intermediate valves with 

 1 slit at each end, the lateral areas comprise two strong ribs with 

 vertically compressed nodules, 8 or 9 to a rib, there is a very nar- 

 row smooth spot on the hardly mucronate jugum, the pleural tracts 

 have near the jugal area 6 or 7 close-set axial threads and be- 

 yond them about the same number of sharp straight axial threads 

 with wider interspaces crossed by much finer, closer, transverse 

 threadlets ; internally the valves are whitish and the sutural laminae 



