Mr. \V. H. Benson on Ianthina, Bolten. 411 



This shell has a more shining surface, and a more convex conoid 

 outline, with a somewhat impressed suture. Morch considers 

 /. roseola, Reeve, found a few degrees further south, near the 

 Nicobars, to be another variety of the type attributed by Chemnitz 

 to the same Gulf. 



/. umbilicata, D'Orb. 



Morch seems to have been in doubt regarding Reeve's figure. 

 Although he cites it without comment among the synonyms of 

 D'Orbigny's shell, yet, under the head of I. globosa, he had 

 quoted it as the probable young of that species. /. umbilicata is 

 referred by Morch to the subgenus Iodina, one of the characters 

 of which is the incised labrum. No trace of this is to be ob- 

 served in Reeve's figure No. 22, from a shell in Mr. Cuming's 

 collection, nor is it alluded to in the description. The conclu- 

 sion to be derived from its appearance in the plate is that it was 

 drawn from a broken shell, the want of correspondence between 

 the right lip and the bifariate strise at the periphery being ob- 

 vious. I have already noticed the deep incision observable in 

 the beautiful and perfect examples from the Atlantic. There is 

 a silky lustre on the surface, which causes the shell to approach 

 in polish nearly to /. nitens, from which the different character 

 of the base and the general form of the shell distinguish it. A 

 pale band is observable round the suture ; and in the large solid 

 variety of the Bay of Bengal, which attains 10 millim. in length, 

 there is also a pale band at the angular periphery. I can find 

 no note of the animal or ovisacs of this species in my journals. 



I. pallida, Harvey. 



The floats are circular and spiral when in good condition; 

 but occasionally the sutural adhesion is lost, and the float, 

 partially uncurling, assumes a semilunar form. The pen- 

 dant cells of eggs are about the size and shape of small apple- 

 pips, rough, and at first pink, but in a more advanced state 

 purplish brown. Independent floats, provided with egg-cells, 

 were also procured; and all the shells with perfect floats were 

 similarly endowed. If Reynell Coates's observations really had 

 reference to /. globosa, Swainson, and not to 7. pallida, the floats 

 of the former shell must be similar in spiral construction to 

 those which I found attached to the latter. 



The rounded base of the columella is not adverted to by Reeve 

 in his description of /. pallida. It constitutes the character of 

 the section Amethystina, Gistel, on which its separation from 

 /. globosa and its allies is grounded. 



Four out of six specimens of the Southern Atlantic form pre- 

 sent a feeble lustre and a spiral sulcate striation, while the other 

 two are deficient in sulcation and are covered with a peculiar 



27* 



