520 APPENDIX. 



RlSSOA STRIATA. (P. 360.) 



Exmouth, July 1854. 



In our original notes it is stated that there is no cirrhus on 

 the opercular lobe at its termination. Having reviewed a 

 fine lively specimen, we found, beyond dispute, a short, white, 

 pointed caudal filament. The pendent minute fillet at the 

 upper and external angle of the aperture is present, though, 

 as it is usually withdrawn, it cannot always be detected. 

 The front of the foot forms a deep labium at the upper part 

 by its separation from the sole ; the flap is of the shape of 

 the letter V inverted, the basal points being in front, and 

 the angular one posterior; it is shadowed out by its flake- 

 white composition, which is visible through the pellucid sole ; 

 but the most singular feature is, that its margins throughout 

 are largely disunited from the upper part of the foot, being 

 only fixed thereon by a central attachment. I have never 

 before observed a similar labial structure, though it may 

 exist in other animals and have escaped notice, for the foot in 

 all the Gasteropoda is more or less labiated. 



RISSOA COSTATA. (P. 362.) 



Our notes are exact; in a specimen examined in July 

 1854, we cannot detect the filament we failed to find in 1852, 

 at the upper angle of the aperture. Can it, instead of pro- 

 ceeding from the mantle, as supposed by us, issue from the 

 neck, and be the genitale of these minute creatures, which are 

 considered bisexual ? It is certainly much lower under the 

 right tentaculum than is usual. If there is any weight in 

 this conjecture, we must conclude that those species and 

 specimens in which the filament is not visible are the females. 

 What militates against these ideas is, that in some of the 

 Rissote we have found the organ in every example. This 

 process is certainly not an edge of the operculigerous lobe 

 that occasionally comes into view. 



i 

 RISSOA SOLUTA. (P. 365.) 



The general colour is hyaline-white, suffused with very 





