l-< IINoi III |..\ l; \ |. -| 1. 1. 1, A. 1 II 



Tin- l'"t i- not produced forward l>ni<';ith tin- h< ad, a- i: 

 Stenoradria, The irills extend from tlic front end of tl 

 within somewhat less than tin- width of a valv from tin- t.iil -, 



I. vii:ii.ri.r> Couthouy. 1M. 17 



Shell small, ohloiiLr, rather elevated and dc-id-dlv ;irinated; 

 creamy yellow, or "of a very pale olive or drab color." Surface 

 smooth to tlio naked eye, but under a lens it is seen to be every- 

 where covered with low granules quincuncially arranged, 

 lateral areas are a trifle raised, but not distinctly so, and upon them 

 the granulation is somewhat effaced, and a few very obsolete radiat- 

 ing sulci are generally distinguishable, as well as several rather 

 strongly indicated growth-periods. "Interior: posterior valve hav- 

 ing 13-14, (rarely 17), anterior valve 14-16, central valve?- 

 slits. Teeth acute, distant; eaves acute, projecting, hardly spot 

 sinus wide, short, flat. Girdle covered with rather large, wide 

 scales, deeply and distantly striated." Length 13, breadth 7 mill. 



Orange Harbor, Terra del Fuego. 



Ch. viriduhis COUTH. MS., GOULD, Proc. Bost. Soc, N. H. ii, p. 

 144, 1846; Otia Conch., p. 5 ; U. S. Expl. Exped., Moll., p. 318; 

 atlas, f. 413. Ischnoradsia viridulas CPU., MS. Lepidopleurus viri- 

 dulus KOCHEBR., Miss. Cape Horn, Polyplacophores, p. 140. 

 'f Minochiton viriduhis Gld., HADDON, Challenger Rep., p. 16,1886. 



A small form, evenly granulated, and having indistinct lateral 

 areas. I have taken the description of the internal parts from 

 Carpenter's MS., as I have not examined the interior of the single 

 specimen before me, which is one of the original lot. 



I. TRIFIDUS Carpenter. PI. 18, fig. 40. 



Shell rather large, rather elevated, regularly oval ; red-ehotnut. 

 maculated with lighter and darker; jugum acute, gothic. Mucro 

 median, flat; entire surface very minutely granulated ; central areas 

 having about 8 strongly punctate lines perpendicular to the jugum ; 

 lateral areas strongly defined, having 2 to 4 obsolete ribs, sonutim.- 

 punctate in the interstices. 



Interior whitish flesh-colored, with two reddish-purple rays diverg- 

 ing from the flat umbones ; posterior valve havin_ r !'>, anterior 

 central valves 2 slits; teeth acute, sometimes serrated at the edge, 

 sometimes striated outside, sometimes smooth. Kaves subspongy ; 

 sinus small, laminate, the lamina slit at the sides and sometimes in 



