NO. 2223. CHITONS FROM THE NORTHWEST PACIFIC— BERRY. 9 



lar where the ribs curve over the jugal tract. Posterior valve with 

 posterior and central areas very sharply delimited by a nearly straight 

 line, the sculpture corresponding to that of the intermediate valves; 

 posterior area with about 20-24 radiating pustulose ribs (pi. 6, fig. 2). 



Girdle wide, averaging about a quarter the width of the median 

 valves. Dorsal scales translucent, strongly convex, loosely imbricat- 

 ing, their convexities as a rule, except in the posterior region, directed 

 obUquely outward and forward (pi. 6, fig. 4); variable in size, but 

 largest near the shell, becoming exceedingly small at the outer mar- 

 gin, while a few scales larger than their immediate neighbors and of 

 a more opaque whitish color occur scattered with no apparent regu- 

 larity among the others. Mounted in balsam some of the smaller 

 scales show a faint striation, but the larger appear ahnost perfectly 

 smooth. Marginal armature comprising quite numerous, very min- 

 ute, finely striate, conical, transparent spines, with a few scattered 

 needle-like spines among them. Ventral scales minute, rectangular, 

 rod-like, very closely ranked in transverse series (pi. 3, fig. 8). 



Color of shell in alcohol a light grayish tan, faintly mottled with 

 cloudings of a ruddier tone. Girdle pale above, with indistinct sutu- 

 ral bands of a darker shade. Entire^ ventral surface of animal and 

 girdle a light pinkish tan. Interior of shell creamy, shading to warm 

 tones of pink and salmon in the deeper regions. 



Radula with strong, unicuspid major laterals, winged minor laterals, 

 and well developed, fan-shaped rhachidian teeth (pi. 3, fig. 9). 



Ctenidia about 28 on each side, extending forward to the second 

 valve. 



Length of entire animal (type-specimen) 21, of shell, 18.5 mm.; 

 width of same 12.5, of shell 8 mm.; maximum width of girdle, 2.5 mm. 



Type.— Cat. No. 215631, U.S.N.M. [S. S. B. 115]. 



Type-locality. — Station 4808,^ 47 fathoms; bottom of sand, shells, 

 and coarse gravel; off Capo Tsiuka, Japan; July 16, 1906 (three speci- 

 mens). 



Remarks. — /. interfossa is a very neat appearing little species and 

 apparently a typical Lepidozona. Though much resembling the pre- 

 ceding species in form and sculpture, the color alone is sufficient for 

 preliminary separation of the specimens, while a more minute exam- 

 ination reveals numerous differences. The special features are the 

 large, smooth, whitish dorsal scales of the girdle; sharply angled 

 jugum; beaked valves; sharply-cut grooves between the ribs of the 

 anterior valve and lateral areas; the number of these ribs; and the 

 very regular, basket-like sculpturing of the central areas, the longi- 

 tudinal riblets being distinctly wider than the intervening spaces. 



Of allied species /. cultratus Carpenter, according to Pilsbry's 

 description, differs from both I. amabilis and /. interfossa in having 



1 These specimens were originally in the same vial as those of /. amabilis, so that here also the station 

 number on the label requires correction. 



