Mr. W. H. Benson on the genus Diplommatina. 329 



this, but the previously homogeneous internal substance of the 

 chlorophyll-band is converted into a sort of frothy mass, like 

 what may be so often observed in the protoplasm of cell-con- 

 tents. The circumstance that the vesicles formed in this way 

 are colourless or only weakly tinged (for this cannot be ac- 

 curately made out), and break out from the interior of the chlo- 

 rophyll-band, through its outer green layer, indicates that the 

 substance of the band is not homogeneous, but that its internal 

 substance especially attracts water, is softer, and more capable 

 of extension than the external substance. These occurrences 

 further tend to show that the green colouring matter is princi- 

 pally, if not exclusively, deposited in the outer layer; but this 

 does not seem to me to be altogether certainly proved, since we 

 cannot decidedly state what are the respective shares which the 

 considerable mechanical expansion, and the original want of 

 colour, bear in producing the colourless or lightly tinted condi- 

 tion of the vesicularly expanded internal substance ; on this 

 point the examination of a transverse section of a band could 

 alone furnish a decided answer, but I know of no means by 

 which this could be obtained and observed in an unaltered con- 

 dition. This much however is certain, that the gi-een colour, if 

 it does not uniformly permeate the whole substance, is still not 

 restricted to a definitely bounded outer layer, since we should 

 see this bounded, at the edge of the band, by a defined line, 



[To be continued.] 



XXIX. — Notice on the question of the presence of an Operculum 

 in the genus Diplommatina, Benson, and description of a new 

 Species. By W. H. Benson, Esq. 



A FURTHER reference to Capt. Hutton on the subject of the 

 operculum of Diplommatina, since the publication of Dr. J. E. 

 Gray's stricture in the July Number of the 'Annals' for 1853, 

 just before my departure from England, having elicited no reply 

 from my correspondent, I proceeded on the 17th instant to a 

 further examination by the gradual destruction of the lower 

 whorls of several specimens of D. folliculus and costulata ; which 

 operation resulted in the detection of the operculum in both 

 species, in which it was found to be withdrawn to a distance of 

 from li to 2 whorls and vipwards from the aperture, so as to 

 render its detection without that process impossible. Encouraged 

 by this success, I have, since then, broken up a couple of spe- 

 cimens of D. Huttoni, Pfr., a reversed species, from Jen-ipani 

 below Mussoorie, and one of my two specimens of a new sini- 

 strorse Australian species, and have been equally successful with 



