Mr. W. H. Benson on Ianthina, Bolten. 405 



LI. — Notes on Ianthina, Bolten ; and Indication of a new 

 Species of the allied oceanic Genus Recluzia, Petit. By 

 W. H. Benson, Esq. 



An examination of Reeve's Monograph of Ianthina, published 

 in 1858, and of Morch's " Materiaux pour servir k PHistoire 

 de la Famille des lanthines" contained in the ' Journal de 

 Conchyliologie ' for the present year, has suggested a few ob- 

 servations with reference especially to the species in an exten- 

 sive collection of pelagian shells made in 1834-35, during a 

 voyage to Calcutta in the { Malcolm/ My success in the con- 

 struction of casting and towing nets of novel patterns, and the 

 inspection of the curious forms captured, caused my example to 

 be followed by other passengers in the ship; an opportunity 

 was thus afforded for the examination of a larger number, and 

 occasionally of finer specimens, of the shells obtained in my own 

 nets, besides two genera which were missed by them. 



The first Ianthina seen were accidentally enclosed in a casting 

 net employed to procure specimens of the brilliant and active 

 little Glaucus Forsteri, and proved to be a small variety of Ian- 

 thina exigua, Lamarck. This species was observed during two 

 days before the island of Madeira was sighted. I succeeded 

 in keeping the animal alive in sea-water for ten days. Glaucus 

 Forsteri lived for a longer period, and was found to feed on its 

 less active shell-bearing fellow-prisoners. 



/, exigua was the most widely distributed species met with, 

 occurring again near the equator, and continuing along the 

 Brazilian portion of the Atlantic, towards the island of Tristan 

 d'Acunha, where it attained a large size, as far as 39° of south 

 latitude. Here it was again small ; but a still larger variety, 

 with a more rosy violet tint, appeared in the middle of the 

 Southern Indian Ocean, north-east of the Isles of St. Paul and 

 Amsterdam. Between this variety and 1. capreolata, Montrouzier, 

 I can find no sufficiently distinguishing character. Smaller 

 specimens again occurred to the south of the equator, and at 

 the head of the Bay of Bengal. 



A small and delicate variety of /. nitens, Menke, made its ap- 

 pearance to the north of the Cape de Verde Islands. South of 

 this group, the apical nucleus of the same species was taken ; 

 and in 6° of north latitude the shell was captured fully grown. 

 The peculiarities of the spire and float will be noticed in another 

 part of this paper. 



In 14° north lat., south of the Cape de Verde Islands, a small 

 shell, which I think must be the young of Reeve's /. Smithia, 

 was found sparingly, as well as at the equator. 



Between 4° and 5° of north lat., /. planispirata, Adams & Reeve 



