ISCHNOCHITON-ISCHNORADSIA. 147 



I. HAKODADENSIS Carpenter, n. sp. PI. 19, figs. 64, 65, 66. 



Shell oval-oblong, moderately elevated, back rather roundly arched, 

 scarcely keeled. Soiled buff, maculated and striped with blackish- 

 brown. 



Lateral areas slightly raised, cut into 6 to 9 low flat unequal 

 riblets by radiating impressed lines, the riblets made uneven by con- 

 centric wrinkles of growth ; central areas very minutely pitted all 

 over, the surface being something between a quincuncial granulation, 

 and a succession of ww-like zigzags. End valves having fine radiat- 

 ing riblets cut by some cencentric growth-sulci. Mucro in front of 

 the middle, rather prominent. 



Interior blue-white ; sinus smooth ; sutural plates low, rounded ; 

 anterior valve having 15-20, central valves 2-3, posterior valve 15 

 narrow slits ; teeth rather sharp, sometimes slightly roughened ; eaves 

 short, narrow, solid. 



Girdle covered with small, solid, convex, smooth scales (fig. 66). 



Length 25, breadth 15 mill. 



Halcodadi, Japan. 



This species, which was collected by Wm. Stimpson of the North 

 Pacific Exploring Expedition, has very much the aspect of Lfruti- 

 cosus Gld. of Australia, the sculpture of the central areas being of 

 the same zigzag character. From all species of the /. longi- 

 cymba group, however, this is distinguished by its smooth, convex 

 girdle scales, and by the plurality of slits in the side insertion-plates. 

 The above description and figures are drawn from part of the 

 original specimens. 



I. ALBKECHTI Schrenck. PI. 19, figs. 70-74. 



Shell large, oval, elevated, the dorsal ridge acute ; mucro median, 

 nearly flat. Reddish maculated with darker, the interior having 

 rays of reddish-brown. 



Entire surface minutely and closely punctate ; central areas with 

 about 30 lines of granules on each side of, and parallel with, the 

 jugum ; lateral areas having in the young 4 to 6, in the adult 10 to 

 12 radiating, distantly granose riblets; the end valves having 50 

 riblets. 



Interior : posterior valve having 12, central valves ? to 3, ante- 

 rior valve about 17 slits ; teeth acute, sometimes rugose or lobed at 

 the edges, outside ; sinus moderate, 8 to 12 dentate. 



