S. t. tenuissimâ, elegantissime sculptâ, lividâ, rufo-fusco pallide maculatâ; anfr. nucl. ii. valde tumidis, lævibus, apice mamillato; dein anfr. norm. iv. tabulatis, suturis fere rectangulatis, supra spiram bi-seu tri-carinatis, carinulis aliis postea intercalantibus; totâ superficie elegantissime et creberrime radiatim lirulatâ, lirulis acutissimis, extantibus, supra carinas subgranulosis, interstitia anfr. primis fenestrantibus, postea decussantibus; basi valde rotundatâ; carinulis circ. v., anticâ granulosâ, sculptâ; umbilico maximo, anfractus intus monstrante, lineis spiralibus circ. iii. distantibus, et lirulis radiantibus à basi continuis, concinne ornato; aperturâ rotundatâ, à carinulis indentatâ, vix parieti attingente, intus iridescente, nacreâ: operculo tenuissimo, multispirali, anfr. circ. x., radiatim eleganter rugulosis. Long. 0.38, long. spir. 0.19, lat. 0.42, div. 85°. _Hab._ Catalina Island, 30-120 fms. 20, both alive and dead. The name _Solariella_, given to a crag fossil (tertiary) species by Searles Wood, which he afterwards reunited to _Margarita_, is here used as a subgenus, in the author’s sense, for _Margaritæ_ with large crenated umbilicus. This is one of the many instances in which the North Pacific fauna carries out the ideas of the English crag. Unfortunately, the name appears in Add. Gen. I, 431, for a subgenus of _Monilea_, with which these shells have only a limited affinity; and, accordingly, the true _Solariellæ_ have been reconstituted as part of _Minolia_, A. Ad. That gentleman, however, fully accords with the present arrangement. The _Solariellæ_ are known from _Trochiscus_, and from all forms of _Solariadæ_, by the normal (not inverted) nuclear whirls; and from the Solarids, by the nacreous texture. Dr. Cooper’s very lovely species of a very lovely group may possibly prove to be a variety of the Japanese “_Minolia aspecta_ A. Ad.” ms. in Mus. Cuming; but, until more specimens from each district have been compared, it is more prudent to keep them separate. It seems to have exhausted the powers of sculpture on its graceful habitation. Under the microscope, the sharp transverse lirulæ, mounting over the keels, dividing the interspaces, and even ascending the wide umbilicus, are eminently beautiful. Even the operculum is sculptured with delicate waved radiating lines. It has the aspect of an extremely thin _Torinia_, with a funnel-shaped umbilicus. This is not only bounded by a granular keel, but has three other distant spiral lines crossing the lirulæ. The radiating sculpture is more distant on the upper whirls, where first two, then three keels appear, fenestrated by the lirulæ, which afterwards become much closer, and are sometimes worn away behind the labrum. MARGARITA Leach, 1819.