SYSTEMATIC 167 



Ianthina globosa Swainson 



1822 Ianthina globosa Swainson, Zool. Illustr. II, pi. 85. 



1828 Ianthina nitens Menke, Synopsis, 84. 



1840 Ianthina rotundata Leach., MS. Dillwyn, Contrib. towards a History of Swansea, 59. 



1840 Ianthina pallida Thompson, Ann. Nat. Hist, v, 96. 



1844 Ianthina patula Phillipi., Moll. Sicil. II, 224, pi. 28, fig. 14. 



1858 Ianthina striolata Rve., Conch. Icon. XI, pi. 5, fig. 24^, b. 



1858 Ianthina iricolor Rve., Conch. Icon, xi, pi. 5, fig. 23 a, b. 



Two species of Ianthina are represented in this collection from the first survey, both occurring 

 together at each of two places. On the second survey, specimens occurred at WS 1057 and WS 1058 

 in surface hand-nets. The samples consist of seven /. ianthina (of planispirata-balteata shape and 

 markings) and four /. globosa (mauve-white to pale pinkish, and probably closest in form to Thompson's 

 pallida). 



From north equatorial waters (o-6° 10' N, 1 1° 25' W), on the northern edge of the Guinea Current, 

 came another sample, four /. ianthina — of the typical ianthina form — and two large typical /. globosa. 

 The Biological Log-book records the presence of the siphonphore Porpita, upon which the Ianthina 

 were feeding. One /. ianthina carried an egg-raft. 



These two species are very distinct, wide-ranging over most seas, and would seem very frequently 

 to occur side by side. 



The systematics of the genus Ianthina are at present in course of full revision by Dr Dan Laursen, 

 who has worked on the extensive Dana material. I have not seen these results, and have therefore in the 

 present account merely assigned the two Benguela species according to the currently accepted view 

 of Iredale (1910), who regarded Ianthina as containing four widely distributed species. The first is 

 ianthina (Linn.) in which Iredale groups planispirata, trochoidea, britannica and depressa. Oliver 

 (19 1 5) considered violacea Bolten to include both communis and balteata, and in addition to these 

 species I have examined roseola, africana and fragilis, as represented in the Winckworth Collection at 

 the British Museum, and would tentatively place all these forms in synonymy with ianthina. 



In shell features, the distinctive characters of this species are evidently its angled periphery and 

 strongly retracted, sharply triangular apertural sinus. Typical specimens of the form ianthina are paler 

 bluish white, above the periphery, and deeper blue below; the chief colour variation in the species is 

 the development of a white band at the central part of the base of the shell, giving the planispirata- 

 balteata pattern, of pale blue above, deep blue around and below the periphery and white at the base. 

 In shell height, depressa and planispirata are the most flattened, africana and trochoidea the most 

 elevated and conical, distinctly higher than broad. 



The second species, globosa Swainson, has a much more delicate shell; the whorls are rounded, the 

 body whorl especially large, and bubble-shaped, with an extremely wide trumpet-shaped aperture in 

 the largest adults. There are rather wavy growth lines and these are gently recurved at the periphery, 

 to give a shallow apertural sinus, rounded or obtusely angled. In some forms, especially pallida, there 

 may be low, rounded, longitudinal striae, best developed on the body whorl. The colour does not vary 

 much, and is usually paler blue or mauve, and almost white in the form pallida. 



The two remaining species recognized by Iredale are exigua and umbilicata. Neither is represented 

 in the Benguela material. 



I have provided outline sketches (Fig. 1) illustrating the leading shell characters of ianthina and 

 globosa. All consideration of radula features, anatomy or life-history has been omitted. These aspects 

 will be dealt with both by Dr Laursen, and also in a forthcoming paper by Professor Graham, on the 



