'Tank Nr. 20. 



Mollusks. A. H e t e r u p o d s ([>. 81;. Pterotrachea (tig. 97), lias a 

 long proboscis and sculls itself rapidly on its back, somewhat 

 similar is the allied Carinaria (fig. 98), less transparent 

 and with a small shell. B. Pteropods (Sea-butterflies, 

 p. 81), flap a pair of transparent wings (Hyalea, fig. 99). 



Fig. 97. Pterotrachea coronal a. 

 /i nat. size. p. 81. 



Fig. 98. Carinaria mediterranea. 

 */2 nat. size. p. 81. 



Fig. 99. Hyalea 



trident at a. 

 nat size. p. 81. 



Besides these pelagic animals there are outside the cylinders 

 various small Octopods (p. 76) , and crawling Mollusks , such as 

 N Tethys (fig. 101) , as large as a hand , spotted with red and 

 brown , * Doris (fig. 100) , as large as a thumb , a tuft at one 

 end, * Aeolis (fig. 102), etc. 



Of Crustaceans various kinds of shrimps (see Tank Nr. 23). 



