THE THECOSOMATA AND GYMNOSOMATA 

 OF THE SIBOGA-EXPEDITION 



BY 



J. J. TESCH 



Utrecht. 



With six plates. 



INTRODUCTION. 



The occurrence of Thecosomata and Gymnosomata, composing together the group ot 

 the so-called "Pteropoda"", in the seas now explored by the Siboga, has been stated only a 

 few times. 



Though OoY and Gaimard, on the voyage of the Astrolabe, already described several 

 species from Amboina, yet the indications and figures of these zoologists are too fragmentarj^ 

 and incomplete, to throw some more light on the knowledge of these animals. 



Afterwards it has been, properly speaking, only the Challenger, which collected specimens 

 from a few places (North of New-Guinea and off the Philippines). Moreover I can mention a 

 Note of V. ScH^ELE (list of literature, Munthe 1886). I have also seen some specimens of 

 Thecosomata from the Sunda Straits and Java Sea (Utrecht Zoological Museum). 



In a study on the geographical distribution of such essentially pelagic animals as the 

 "Pteropoda" are, I have preferred to take a larger field of exploration than the area in which 

 the Siboga-material was collected. 



For that reason I have accepted the Australasian province, proposed by Pelseneer ^) 

 (almost agreeing with the Indian province of Kefersteix -), viz. the East-Indian Archipelago, 

 the China Sea, the Philippines and the seas of North-Australia. 



1) Challenger Report. LVIII, p. 62. 



2) In Bronn's Thierreich. Bd. Ill, p. 1135. 

 SIBOGA-EXPEDITIE LII. 



