MADEIRAN GROUP. 93 



fications of each other. Indeed the portosanctana belongs to 

 a rather different type (characteristic of Beck's section Campy- 

 Icea), in which the nmbilicus is open, and the tendency of the 

 surface is to be very minutely hispid or pilose ; whereas in 

 Cryptaxis, Lowe, which embraces the other two forms, the 

 umbilicus is closed up (at any rate in the adult shells), and the 

 surface, although more or less malleated or uneven, is glabrous : 

 and it will be gathered therefore from this circumstance, that 

 the exponents from Madeira proper and the Desertas are more 

 nearly akin inter se than they are to the one from Porto Santo. 



The H. Vulcania has been found hitherto only on the 

 Northern and Central Desertas,^ its place on the southern 

 island being supplied by the very intimately related (but more 

 largely developed) H. leonma — which likewise makes its ap- 

 pearance towards the southern extremity of the Central Deserta 

 (or Deserta Grrande). And indeed were it not for this last- 

 mentioned fact, I should certainly have been inclined to treat 

 the H. leonina as a mere enlarged and exaggerated phasis (or 

 insular modification) of the Vulcania ; but since the two forms 

 co-exist on the central island, that conclusion would hardly be 

 tenable. Nevertheless I am by no means satisfied that the 

 H. leonina is more in reality than the (locally) Tnore southern 

 aspect of the Vulcania, for it must be admitted that we have a 

 very gradual and curious progression, as regards contour, from 

 the Northern Deserta (or Ilheo Cliao) to the southern one (or 

 Bugio), — the examples from the former of those islands being a 

 little flatter and less malleated than the ones (equally referable 

 to the Vulcania. proper) from the Deserta Grrande ; whilst the 

 characters of the leonina, which makes its first appearance 

 towards the southern end of the Deserta Grrande, and which 

 reigns supreme on the Bugio, are merely those of the H. Vul- 

 cania but {particularly on the southern island) exaggerated. 

 However since both the Vulcania and leonina exist on the 

 Deserta Grrande, I think that we may practically refuse to 

 treat them as insular states of each other, and may so find it 

 more convenient to register them as distinct. 



The H. Vtdcania (and leonina) may be said, in a general 

 sense, to combine the fasciated surface of the portosanctana 

 with the closed-up umbilicus and more or less malleated sculp- 

 ture of the Madeiran H. undata. However, the lower band, 

 which is nearly always present in the portosanctana, is in the 



' The Baron Paiva cites the Southern Deserta also for the //. Vulcania. ; 

 but since his material was never obtained by himself, but was brought to 

 him by paid collectors (who were neither over-accurate nor over-scrupulous), 

 I cannot without further evidence place any reliance on that jjarticular 

 Itahitat. 



