834 



PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



Lesson's plate, tinted the brancliifie, the median line, and the sides. 

 As preserved, tlie transparency of the body is only broken by scattered 

 opaque whitish dots, while its gelatinous substance permits the 

 stomach within, and the sludl beyond, to be plainly seen through it. 

 The external surface is roughened by small pimples. As a whole, the 



^.^^ 



1. Female Pterosoma, seen from above. 



2. Shell of the same, seen from beneath, showiuo^ brauchia; protrucliug ; also 



embryonic shell seen at right angles to the other. 



3. Portion of railula of Jfterosoma. 



4. Foot of male Pterosoma. On the posterior crest is shown the sncker, anteriorly 



the external genitalia. Drawings variously enlarged and reproduced from 

 the pen sketches of the writer. 



creature is somewhat fiddle-shaped ; the body consisting of an ellipse 

 that is emargmate anteriorly, and produced into a tail posteriorly, the 

 wing-like expansions do not thin out at the edges, the body proper is 

 cylindi'ical, and e.\tends from tlu; anterior emargiuation towards tin- 



