4 AUGUSTA ÄRNBÅCK-CHRIST1E-LINDE, NORTHERN AND ARCTIC INVERTEBRATES. 



the Siyelidae, but unites the former family with the Botryllidae — has not yet 

 been thoroughly investigated. And t hat is one more reason why I prefer to maintain, 

 for the present, the separation of the three groups into three families. 



A revision of the Styelidae especially a division of the genus Styela based on 

 the relation of the testis to the ovary in the gonad has long been a desideratum. 

 Huntsman (1913) has made an attempt at it, dividing Styela into five genera: Styela, 

 Kalatropa, Goniocarpa, Botryorchis, which form one group, and Cnemidocarpa which 

 forms the other group. The classification proposed by Huntsman is accepted in as 

 much as the genus Cnemidocarpa is adopted. With regard to the systematical posi- 

 tion of Pelonaia corrugata I agree to the view of Huntsman (1912 p. 157). This 

 genus is thus included in the family and not placed in a separate sub-family. 



With the above-mentioned exceptions the system as well as the nomenclature 

 used by Hartmeyer in »Bronn's Klassen und Ordnungen des Tierreichs» with the 

 changes proposed in » Ascidiarum nomina conservanda» (1915) is adopted in this paper. 



In the following synopsis of genera and species an attempt has been made to 

 group species related to each other. The synopsis is based on anatomical characters 

 especially those which are exhibited by the branchial sac and the reproductive organs. 

 In identifying the species those two organ systems have proved to present more 

 valuable characters than the others. External features are only secondarily used. 



A new genus, Ypsilocarpa, has been established for an Arctic form which seems 

 to be allied to Cnemidocarpa. Four new species have been described viz., Styela 

 theeli, Cnemidocarpa mollispina, Cnemidocarpa cirrala, Ypsilocarpa clipeata. 



In the present paper, the reproductive organs of Kukenihalia borealis are de- 

 scribed. They are of a structure which highly differs from that of the corresponding 

 organs in other known Polyzoids. The development of a brood-pouch is especially 

 noticeable. The organs in question have hitherto been unknown. 



Special notes concerning the geographical and bathymetrical distribution have 

 been made in the remarks on the different species. 



The occurrence of such forms as Styela theeli in Samlenfjord and Cnemidocarpa 

 rhizopus in Cattegat is remarkable, likewise the catch of Pelonaia corrugata in Gull- 

 marn. P. corrugata has even been found on the west and south coasts of Norway. 

 According to the investigations of Norwegian zoologists (M. Särs 1866, Grieg 1913), 

 it belongs to the Arctic relic fauna which has been observed in the Norwegian fjords, 

 a view which is not unquestionable as will be shown in the following. lts occurrence 

 off Bohuslän is probably accidental. It has no doubt been brought there by the 

 cold water which, orginating from the North Atlantic, has been observed to fill 

 Gullmarn in Spring. 



In Gullmarn there exists an abundant Ascidian fauna. As the present paper 

 is dealing with two Ascidian families only, it can but give a small idea of the 

 richness of the Ascidian fauna in those waters. 



As to synonyms only those names have been mentioned which are thought to 

 be more commonly known. As complete lists of works have already been published, 



