Tank Nr. 20. 



35 



Mollusks. A. Heteropods (p. 81). Pterotrachea (fig. 97), has 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 (Hyalaea, fig. 99). 



Fig. 97. Pterotrachea coronata, 

 1/2 nat. size. p. 81. 



Fig. 98. Carinaria mediterranean 

 '/^ nat. size. p. 81. 



Fig. 99. Hyalaea 

 tridentata. p. 81. 



Besides these pelagic animals there are outside the cylinders 

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

 as *Tethi/H (fig. 101), as large as a hand, spotted with red and 

 brown, *lJorh (fig. KX)) , as large as a thumb, a tuft at one 

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



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



