KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 63. NIO 2 43 



the left. Moreover, rudiments of one or two other folds have been observed in some 

 individ uals, on one side or on both sides. According to him, the development of 

 the branchial folds has a relation to the age of the individual: >On trouverait donc 

 chez Styelopsis, suivant 1'åge des individus, suivant les variations des individus ou 

 des variétés, toutes les transitions entré le manque total des replis et la présence 

 d'au moins un repli vrai de chaque cöté» (1. c. p. 187). 



In well-developed specimens from Gullmarn, Bohuslän, one fold is present on 

 the right side, none on the left, and the longitudinal vessels are arranged in groups, 

 each group comprising 3 — 5 longitudinal vessels. 



Even as regards the external appearance D. grossularia proves to be a highly 

 variable species. This is clearly shovvn from figs. 34—37, illustrating 4 specimens, 

 dredged at the same time and at the same locality, Kobbe Bay, Spitzbergen. Fig. 

 34 shows an individual of a high and rounded, almost globular body-form, having 

 the test almost smooth and the apertures level with the surface. Fig. 37 shows an 

 individual of quite another type, having the body greatly flattened, dorso-ventrally, 

 and the test coarsely wrinkled. On figs. 35 — 36 specimens with a more or less 

 wrinkled test and prominent apertures are shown. 



D. grossularia has its centre of distribution in the Boreal region and is com- 

 mon along the coasts of north-western Europé, especially on the coasts of the North 

 Sea waters ; it is abundant in the Danish sounds and on the Swedish west coast in 

 Gullmarf jorden; it also occurs in the south-western part of the Baltic Sea. In the 

 eastern Boreoarctic mixture zone it is sparingly met with, but it is common on the 

 American Atlantic coast in many places. In the Arctic region it has been recorded 

 from several localities, but in few specimens. 



D. grossularia occurs both solitary and aggregated into groups. It inhabits 

 bottoms of clay or sand with stones, shells and algae. It is often attached to stones 

 and shells and other Ascidians especially Polycarpa pomaria. It occurs in shallow 

 water as well as in water of considerable depth, down to 660 m. 



Dendrodoa aggregata Rathke 1806. 



Pl. 2, figs. 39 — 40. Pl. 3, figs. 43-44. 



Syn. Cynthia aggregata, Särs 1858. 



Dendrodoa glandaria, Herdman 1891. 

 Styela aggregata, Kiaer 1893, 1896. 



Uabitat. 



Norway: Finmarken, without definite locality, 4 sps (Loven). — D:o Hammer- 

 fest, 30 fms, sandy bottom, 8 sps. — D:o, Grötsund, 30 — 70 fms, clay and stones, 

 a great number of specimens; in the neighbourhood of Tromsö, 1 sp; D:o off Karlsö 

 50 fms, 5 sps (October 1861, Goés a. Malmgren). — D:o Karlsö, 30 — 40 fms, many 

 sps (June 13, 1864, I. A. Malmgren). 



ledand: Berufjord, 15 — 30 fms, a great number of specimens (Torell). 



