198 Description of the Plates. 



For a full account of the anatomy of the organ, see Langer, 

 Denkschriften Akad. Wiss. Wien. xii., Bd. 1856, p. 39, Taf. i., 

 figs. 3 and 4. 



For figures of the muscular system, see Poli, Testacea Utriusque 

 Sieiliae, tab. ix., fig. 2 ; and for the heart and rectum, the 

 same plate, fig. 13 ; and Langer, l. c, Taf. ii., fig. 8. 



For an explanation of the route taken by the ova and spermatozoa, 

 in these dioecious animals, see V. Baer, MeckeFs Archiv., 

 1830, p. 313; and also V. Hessling, Zeitschriffc Wissenschaft 

 Zoologie, X., i860, p. 358. 



For the various parts of the Lamellibranehiate organism, which in 

 different species may be modified so as to serve as marsupia 

 for the lodgment of ova and embryos, see Bronn, Klassen und 

 Ordnungen des Thier-reichs, Bd. iii., p. 442, ibique citata. 



