MARGARITA. 301 



of the spirals. Suture well marked, angulated, but not sharply so. 

 Mouth rather oblique, rounded, hardly angulated at the upper 

 corner, not in the least descending, brilliantly iridescent within and 

 showing the colored spirals of the outside. Outer lip thin, slightly 

 puckered at the spirals, a little thickened on the base. Inner lip 

 thickened and reflected, especially at its junction with the body 

 where it almost covers the umbilicus. The pillar is much curved, 

 and thins gradually out to its junction with the base. The um- 

 bilicus is large and funnel-shaped on the base, deep, but small 

 further in, contracted by a spiral white pillar-pad, and more than 

 half covered over by the pillar-lip. Operculum rather thin, horny, 

 yellow, with ten or twelve very gradual turns, which are strongly 

 defined by a thickened line ; it is feebly marked with concentric 

 and with radiating lines. 



Alt. 0-77 in., diam. O78, least 0'66. Penultimate whorl, 0'2. 

 Mouth, height 0'4, breadth (M. ( Watson.) 



There is a Margarita striata, Leach (nee Linn, nee Brod.) which 

 this resembles, but the Kergueleu species is very much more 

 flattened and broader, and much more contracted in the spire. 



The variety ccerulrus (fig. 55) differs from the type in having 

 only four spiral threads above the periphery, while on the base 

 below the peripheral thread the threads are also fewer, and are 

 flattened out till they are barely parted by narrow lines of irides- 

 cent white. With the exception of these and the white umbilicus, 

 the base is of an intense blue-black gray. The comparative absence 

 of the spirals on the upper part of the whorls gives a flatness to the 

 aspect of the shell below the suture, while the strength of the second 

 and fourth spirals gives an angulation to the whorls that is apt to 

 mislead the eye, the more so that the only specimen of this variety 

 has the whole spire completely covered with Polyzoa. In spite 

 however, of its deceptive appearance, I am pursuaded that this is 

 only a variety of Trochus charopus, the more so that the marking 

 on the embryonic whorl are identical. 



In form this variety especially recalls Margarita polaris, Beck 

 (Geneva Mus. Coll. Delessert), as also in its distant rather sharp 

 spirals and half covered umbilicus, but it is more depressed on the 

 base and flattened below the suture ; the whorls are of much more 



