506 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.55. 



ISCHNOCHITON OPHIODERIVIA, new species. 



Chiton oval, dull flesh color, with greenish flecks, internally bluish 

 green, girdle with oval white convex smooth scales of about equal size, 

 the back low, rounded; anterior valve less than semicircular, with 

 impressed incremental lines, the surface covered with flat rectangular 

 or lozenge-shaped scalelike sculpture resembling snake skin, internally 

 with nine slits, and smooth insertion plates; posterior valve with the 

 mucro moderately prominent, in front of the center, the posterior 

 tract sculptured like the head valve, the central area with extremely 

 fine, somewhat oblique axial threadlets crossed by incremental lines; 

 internally with nine slits, a rather wide straight-edged sinus and quite 

 narrow sutural laminae; intermediate valves with no differentiated 

 jugum, that area and the pleural tracts continuous, sculptured with a 

 very fine oblique reticulation ; lateral areas with the " snake-skin " 

 sculpture, without ribs; internally with one slit at each end, a wide 

 straight-edged sinus and arcuate sutural laminae. Length, 15 ; width. 

 12 ; height, 4 mm. 



Eabifat—Punnmfi, James Zetek (No. 574). Cat. No. 332145. 

 TJ.S.N.M. The " snake-skin " sculpture recalls that on Acanthochi- 

 tona^ but is more compact. 



ISCHNOCHITON ACELIDOTUS, new species. 



Chiton whitish, of moderate size, with high but not keeled back, 

 the entire surface except the lateral areas covered with a microscopic 

 oblique reticulation; the girdle provided with densely set small spi- 

 nules, whose distal ends appear at the surface to form a regular pave- 

 ment of small lozenge-shaped scales; the gill rows advance to the 

 second valve ; anterior valve smooth, except for the microscopic decus- 

 sation, internally with 14 slits; posterior valve with the same number, 

 the mucro in front of the center, the posterior tract sculptured like the 

 anterior valve, the central area like the intermediate valves; the latter 

 have a smooth space in the mucronate jugal area, the pleural 

 tracts have six to eight widely spaced slender axial threads ; the lateral 

 areas incremental lines and extremely minute pustulation. Length, 

 14 ; M idth, 9 ; height, 5 mm. 



Hahitat. — Magellan Straits in 77^ fathoms, ooze, bottom tempera- 

 ture 46.9°, United States Fish Commission steamer Albatross. 

 Cat. No. 122731, U.S.N.M. 



ISCHNOCHITON MARIPOSA, new species. 



Chiton small, profusely marbled with red, white, green, and gray, 

 the pattern different in each specimen, the anterior and second valve 

 conspicuously longer axially and somewhat higher than those suc- 

 ceeding them, the girdle maculated with alternate lighter and darker 

 patches; the back rather low, not forming a ridge at the jugum; 



