KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 63. NIO 2. 5 



only the papers referred to are here enumerated. The measures have been taken on 

 preserved specimens. 



To the eminent artist Georg Liljevall I wish to express my most sincere 

 thanks for his excellent and delicate drawings. 



Revised species. 



Some of the Ascidians collected by the Vega Expedition, 1878—1880, have 

 been described by Swederus in 1885. A re-examination of the material has given 

 the following result: 



The numerous specimens labelled and described by the above-mentioned author 

 under the name of Molgula ampulloides van Ben. do not belong to this species. They 

 have been identified partly as Molgula chrystallina Möller, partly as Rhizomol- 

 gula sp. 



Molgula ampulloides van Ben. is not represented among the material dredged 

 by the Vega Expedition in the Arctic Sea of Siberia and in Bering Sea. Thus any 

 report of the species from those localities is erroneous as far as it is based on the 

 statement of the above-mentioned author. 



Boltenia spec? Swederus is no Boltenia which evidently appears from the 

 description. In all probability it is Molgula retortiformis Verrill. Very large speci- 

 mens of this form have been collected by the Vega Expedition in the Arctic Sea of 

 Siberia. 



Styela conica Swederus is certainly no nevv form. The author describes a 

 Styelid with one sinuous ovary on each side of the body and a pyramid-shaped 

 process betvveen the apertures. Judging from the description it should then be Styela 

 rustica; but this species is not represented in the material of the Vega Expedition. 

 The original has not been found again. 



Styela arctica Swederus is probably synonymous with some form of Dendrodoa. 

 The two specimens described might belong to the species D. aggregata which has 

 been collected in Bering Sea by the expedition in question. The originals have not 

 been found again. 



Styela pomaria Sav. = Polycarpa pomaria Sav. is not found among the Asci- 

 dians dredged by the Vega Expedition. The originals have not been found again. 



Rightly identified species are the following: 



Boltenia bolteni L. = Boltenia ovifera L. from the Bering Sea. 



Cynthia echinata L. = Boltenia echinata L. from the Arctic Sea of Siberia. 



Chelyosoma macleayanum Bröd. a. Sow. from the Arctic Sea of Siberia. 



Synoicum turgens Phipps from the Bering Sea. 



Nordenskiöld's Expeditions, 1875 and 1876, have brought back to us Asci- 

 dians from Novaja Zemlja and the Yenissej. A few species have been reported by 

 Leche (1878) in his paper on the marine Mollusca collected by the above-mentioned 

 expeditions. From a re-examination it appears that the species labelled Molgula 



