EEPOET ON THE GASTEEOPODA. 79 



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

 gradually out to its junction with the base. The umbilicus 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 

 to twelve very gradual turns, which are strongly defined by a thickened line ; it is feebly 

 marked with concentric and with radiating lines. H. 0'77 in. B. 0'78, least 0'66. Pen- 

 ultimate whorl, 0"2. Mouth, height 0'4, breadth 0'4. 



There is a Margarita striata, Leach (ncc Linn, ncc Brod.), which this resembles, but the Ker- 

 guelen species is very much more flattened and broader, and much more contracted in the spire. 



The variety (fig. 6b) 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 iridescent white. With the exception of these and the white umbilicus, 

 the base is of an intense blue-black grey. 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 persuaded that this is only a variety of Trochus 

 charopus, the more so that the markings 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 rapid increase, the spirals on the 

 base are very much more numerous, and the shell is brilliant in polish and in colour. 



45. Trochus {Margarita) pompholugotus, 1 Watson (PI. V. fig. 9). 



Trochus (Margarita) pompholugotus, Watson, Prelim. Eeport, pt. 4, Journ. Linn. Soc. Lond., vol. xiv. 



p. 702. 



Station 24. March 25, 1873. Lat. 18° 38' 30" N., long. 65° 5' 30" W. North of Culebra 

 Island, West Indies. 390 fathoms. Pteropod ooze. 



Shell. — Depressedly globose, with a low turreted spire, thin, opaque, chalky, rough, 

 umbilicate. Sculpture : There are of spirals on the last whorl about forty, low, rounded, 

 very unequal, some being very minute, one or two above the periphery stronger than the 

 rest ; the lowest of all is much the strongest, and defines the umbilicus, within which the 

 whole sculpture increases in distinctness ; on the penultimate whorl there are about twelve 

 spirals fully stronger than on the last. The furrows are broader than the threads, but as 

 they widen are occupied by a minute intermediate thread. Longitudinally these spirals 

 and furrows are crossed by much finer and sharper oblique threads, which in general are 

 much narrower than their interstices ; but towards the mouth, where all the sculpture 



1 ■xofi.&'KvyuTos, bubble-shaped. 



