1890.] MARINE MOLLUSCA OF ST. HELENA. 2"! 



lines also form two or three spiral bands. The thickened border of 

 the umbilicus is not stained with brown so distinctly as in M. alderi. 

 The operculum is at present unknown. 



Natica (Poltnices) porcellana, d'Orbigny. 



Hab. Teneriffe, Madeira, Cape Verde Islands. 



This species and N. uherina of the same author from the "West 

 Indies are very closely related, but the majority of specimens of the 

 latter have a differently formed callus. The figure in Sagra's ' Hist. 

 Cuba ' (pi. xvii. fig. 19) represents an umbilical callus very like that 

 of N. porcellana, but in most West-Indian specimens it has not got 

 such a central prominence at the termination of the umbilical ridge, 

 and consequently a less marked sinus above it. 



All the specimens from St. Helena are much smaller than the type 

 figured by d'Orbigny (Webb & Berthelot's Hist. Nat. Canaries, 

 Mollusques, pi. vi. figs. 27, 28). 



The umbilicus also in these specimens is unusually large, the 

 groove within it deep, and the curved ridge is rather sharp. In the 

 specimen oi N. porcellana figured by Reeve (Conch. Icon. figs. 102 



a, b) the umbilicus is much narrower and the callosity more 

 developed. In the Museum Collection there are two specimens 

 from Goree, named N. loveni, Dunker, which undoubtedly belong to 

 this species, but at present I have not met with any description of 

 that species. The operculum is thin, homy, and reddish. In his 

 list of St. Helena shells Jeffreys quotes N. nitida, Donovan. We 

 did not receive this shell from Mr. Melliss ; but it is possible it may 

 have been the present species, which is not unlike Donovan's figure*. 



Ianthina communis, Lamarck. 



Hah. East and West Atlantic. 



This species appears in Jeffreys's list of Mr. Melliss's St. Helena 

 shells under the name of I.fragilis. The form and colour varies 

 considerably in the seven specimens from the shores of St. Helena. 

 Some^ are as depressed as I. ccerulcata. Reeve (Conch. Icon. figs. 

 7a, 7b), and similarly coloured, whilst others are much more 

 elevated, nearly as high in the spire as /. ajricana, Reeve, fig. S a, 



b, and white above as in that species, which is also considered'^but a 

 variety of the present species by Sowerby (Thesaurus, v. p. ,t6). 

 I. bicolor, Lesson ', also described and figured from St. Helena 

 specimens, belongs to this species. 



Ianthina globosa, Swainson. 



Hab. St. Helena (Lesson). 



This species is described and figured by Lesson, from examples 

 taken at St. Helena, under the name of /. prolovguta, Blainvdle 

 {vide Voy. Coquille, Zool. vol. ii. p. 3G(i). 



1 Zool. Voy. Coquille, vol. ii. p. DGa. 



19* 



