294 MARGARITA. 



width of their interstices. Sometimes there are still more delicate 

 secondary threads between them. Of the first I count 10-12 on the 

 penultimate whorl. Upon the base of the last whorl the ridges 

 become broader and broader. In the vicinity of the umbilicus they 

 exceed double the breadth of the intervening furrows. The layer 

 which this sculpture principally composes, is for the rest only about 

 the thickness of a coat of varnish ; and beneath it, showing very 

 slight traces of longitudinal striae, appears silvery mother-of-pearl, 

 which shines on the whorls of many specimens while still living. The 

 most usual color is a dark slate-gray, through which the pearly 

 layer, as through a heavy gauze, faintly shines. But if one still 

 closer follows the color-changes, we find upon the pearly layer 

 a thick yellow one, visible also from outside on the base, for it 

 extends over the whole umbilical tract as far as the inner lip. 

 Usually this yellow tract merges into the ground color around its 

 circumference ; more seldom it is sharply defined. In some speci- 

 mens this yellow color predominates over the whole shell. But 

 usually it is covered by the slate-color, which on the base through 

 separated flames passes into the above-described yellow umbilical 

 spot. (Midd.) 



The T. modedus of Midd., seems to me to be very closely allied, 

 perhaps only a variety. The name is preoccupied by Philippi. The 

 description, translated in fidl, is as follows: 



T. modestus Midd. (pi. 47, figs. 89-91). Shell couoidal, apex 

 acute, reddish-brown, encircled by elevated lurid lines ; when decor- 

 ticated the stratum beneath is pearly, azure. AVhorls little convex, 

 encircled by sharply cut longitudinal [spiral] striie ; last whorl sub- 

 angulate, base couvexo-plane, concentrically striate ; aperture sub- 

 orbicular, pearly, white ; umbilicus closed. 



Alt. 15, diam. 14 mill. (Midd.). 



The elevated sculpture strife which encircle the whorls, are very 

 clearly cut on the entire spire, double as narrow as the intervening 

 furrows ; 6-7 are upon the penultimate, 5 on the antepenultimate, 

 and 4 on the next earlier whorl ; 10 strite encircle the last whorl 

 above, and as many upon the base ; the innermost of the latter 

 extend to the columella, and a few of them are also visible within 

 the aperture. The interstices between the stride are brown-red, and 

 sometimes have a trace of a secondary thread. The elevated stripe 



