ISCHNOCHITON. 



Trachydermon flectens CPR., Rep. Brit. Asso. Adv. Sci. 1863, p. 

 649 - Isehnochiton ( Trachydermon') flectens CPR., Proc. Acad. Nat 

 Sci. Phila. 1865, p. 60. 



A variety from Catalina Is. has the posterior valve with 7, inter- 

 mediate 1, anterior 8 slits, the mucro less anterior ; divergence 90 



I. LIVIDUS Middendorff. PL 6, figs. 22, 23, 24. 



Shell elevated, tegrnentum smooth, shining, livid. Anterior 

 valve, lateral areas and posterior valve obsoletely radiately rib- 

 striate. Central areas longitudinally costulate, the riblets sepa- 

 rated, sharply cut, whitish, 18-20 in number. Lateral areas 

 depressed. Gills median. 



Length 23 mill.; divergence 120. 



Sitka. 



Chiton (Stenosemus) lividus MIDD., Beitr. zu einer Ma'lac. Ros- 

 sica, i, p. 124, t. 13, f. 3, 4. 



This species and the next have not been found by later observers. 



I. SCROBICULATUS Middendorff. PI. 8, figs. 66, 67, 68. 



Shell depressed, tegmentum rough, opaque, ashen or yellow- 

 brown. Central areas regularly pitted in longitudinal series ; lat- 

 eral areas swollen, divided by a radiating groove which widens 

 below. Girdle having narrow scales. Gills median, 16 in number. 



Length 9 mill.; divergence about 130. 



California. 



Chiton (Stenosemus) scrobiculatus MIDD., Mai Ross i p 127 t 

 14, f. 4-7. 



I. SOLIDIOR Carpenter, n. sp. Unfigured. 



Shell small, oval, somewhat elevated, rather flesh-colored; jugum 

 obtuse ; mucro elevated, in front of the middle. Valves pointed, a 

 little rounded at the margins; lateral areas scarcely defined. 

 Entire surface smooth, under a lens minutely roughened and very 

 minutely punctate ; wrinkles of growth conspicuous. 



Inside : posterior valve with 9, anterior with 8, median with 1 

 slit; the teeth obtuse, solid, much separated, at times somewhat 

 roughened. Sinus wide, flat ; eaves short. 



Girdle normal for Trachydermon, the granules solid. 



Philippines. 



