492 
MR. H. N. RIDLEY ON THE 
former * that T. cyclostoma , T. nubila , T. cylindracea , and the 
present species are mere varieties of one and the same form. 
25. Ianthina eragilis, Lamarck. 
Of the various species figured by Reeve, that which he has 
identified as Lamarck’s I.frayilis (Conch. Icon. pi. ii. ff. Ga, 6 b) 
closely resembles the shells from Fernando Noronha. They have 
the same perpendicular columella and the same division of colour, 
the “ deep-violet ” tint of the base terminating abruptly at the 
periphery. 
26. Cerithium atratum {Born). 
Hab. "West Indies, Pernambuco, and Rio Janeiro {Brit. Mus.). 
I regard the G. caudatum of Sowerby as undoubtedly belonging 
to this species. “ Sicily,” the locality assigned by Sowerby in the 
‘ Thesaurus Conchyliorum ’ and in Reeve’s ‘ Conchologia Iconica ’ 
to G. atratum , is evidently incorrect. 
27. Mitrularia alveolata {A. Adams). 
Calyptrsea alveolata, A. Adams, Reeve, Con. Icon. vol. xi. pi. 3. ff. 8 a-b. 
Hab. Galapagos Islands {Beeve) ; St. Kitts, West Indies 
{Brit. Mus.). 
The single shell from Fernando Noronha possesses all the 
characteristics of the type from the Galapagos Islands. The 
specimens from Fernando Noronha, assigned with doubt to M. 
uncinata , Reeve, by Watson t, in all probability belong to the 
same species as that collected by Mr. Ridley. They are, how- 
ever, only young specimens, so that their determination is all the 
more difficult. 
28. Hipponyx antiquatus {Linne). 
Hipponyx antiquatus (L.), Fischer, Journ.de Conch, vol. x. p. 5, pi. ii. 
ff. 1-9 (anatomy); Crosse, Journ. de Conch, vol. x. p. 20; Morch, Malak. 
Bldtt. vol. xxiv. p. 98. 
Hab. West Indies ; islands of Ascension, St. Helena, and 
Trinidad in the South Atlantic, Peru and California ( Brit. Mus.). 
The single specimen from Fernando Noronha has the spire 
more recurved than any other specimen I have seen and it is 
inclined to the left. 
* Conch.-Cab., Solarium, p. 26. 
t ‘Challenger’ Gastropoda, p. 461. 
