MARGARITA. 295 



themselves are brownish-yellow, when the very thin layer of colored 

 calcareous matter is eroded, a beautiful azure-blue nacre is revealed. 



Sitka. 



This species I have not seen. It may belong near Gibbula fulgens 

 Old., perhaps. 



I do not know whether Sowerby had the true modestus of Midd., 

 or not. His figure is copied on pi., 37, fig. 8. His monograph of 

 Margarita in Reeve's Iconica contains more blunders than any work 

 I have ever seen, unless some other papers by the same author prove 

 to be exceptions. 



M. PUPILLA Gould. PI. 44, figs. 29-32. 



Shell narrowly umbilicated, conical, solid, lusterless, ashen or 

 whitish ; surface spirally traversed by unequal cord-like lira?, sepa- 

 rated by sharply crispate-striate interspaces, as wide or wider than 

 the ridges. The latter are nearly smooth or show traces of the 

 oblique striation ; upon the last H whorls there is usually a spiral 

 thread in the inter-liral spaces ; above this there are 4 or 5 lirse 

 on each whorl. Upon the base the concentric riblets decrease regu- 

 larly in size from the center outward, and number about 12. The 

 spire is elevated ; apex subacute ; sutures impressed ; whorls 6, con- 

 vex, the* last obtusely angled, flattened beneath ; aperture very 

 oblique, rounded, iridescent inside ; peristome simple, columella 

 arcuate, subreflexed at the umbilicus, often nearly closing it, united 

 with the upper termination of the lip by a parietal callous ; umbilicus 

 bounded by a carina, funnel-shaped, its perforation very small. 



Alt. 13, diam. 12 mill. 



Alaska to Monterey, Cal. 



Trochus pupillus GOULD, Proc, Bost Soc. N. H. iii, p. 91 (1850). 

 U. S. Expl. Exped., Moll, and Shells, p. 186, atlas, f. 208 (not 

 Cantharidus pupillus ' Gld.' HUTTON, Proc. Linn. Soc. N. S. W. ix, 

 p. 362, and other places). Margarita pupilla of CARPENTER and 

 American authors generally. DALL, Am. Journ. Conch, vii, p. 127. 

 M. calostoma A. AD., P. Z. S. 1851, p. 190. M. wflata CARPEN- 

 TER, Proc. Acad. N. S. Phi la. 1865, p. 62. M. mlmonea CARPENTER, 

 Proc. Cal. Acad. N. Sci. iii, p. 158 (1864). 



A very variable shell. Southward the color becomes deeper, of 

 a salmon hue, and the sculpture finer. Compare Tr. modestus Midd., 

 and Tr. beechyanus von Martens. 



