KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 63. N:0 2. 1'5 



to S. rustica, has been recorded by Ritter (1913) from the Bering Sea. If we 

 compare the descriptions of the two species, it is evident that they differ in only 

 tvvo points: as to the intestine which is of great length, form ing at least two con- 

 volutions in S. macrenteron, and the internal vessels which are of greater number in 

 the last-mentioned species. In all other essential respects they agree. The question 

 therefore arises whether S. macrenteron is to be regarded not as a distinct species 

 but as a variety of S. rustica. 



The largest individuals in the collection are dredged off Spitzbergen and mea- 

 sure about 80 mm in height (baso-apical). The specimens collected off the Swedish 

 coast do not equal the Arctic ones in size; they are not beyond 50 mm in height. 

 Those from the Norwegian coast are often larger. In Tromsösund specimens have 

 been collected measuring 70 mm in height (Bjerkan 1908). 



Styela rustica is most widely distributed in the Arctic region, where it is almost 

 circumpolar. From the Arctic its distribution extends along the Norwegian coast into 

 the eastern Boreal zone to Travemunde in the Baltic Sea on the south, being common 

 off the Swedish west coast, especially in Gullmarfjorden, and the Danish Islands. As 

 far as is known, it has not been recorded from the British Isles. On the east cost 

 of N. America it has been collected in the northern part of the Boreoarctic mixture zone. 



S. rustica inhabits various bottoms, generally rocks and gravel, but also clay 

 and mud with stones. It has been dredged from 2 to 432 m. 



Styela loveni Särs 1851. 



Pl. 1, figs. 3—4. 



Syn. Cynthia coriacea, Aldek a. Hancock 1848. 

 » rustica, Kupffer 1875. 

 Styela aggregata, Traustedt 1880. 

 Tethyum loveni, Hartmeyer in Bronns Tierreich. 

 » coriaceum, Van Name, 1912. 



Habitat. 



West coast of Sweden: Bohuslän, no definite locality, 1 sp (Loven), 2 sps 

 (Olsson 1869). — Gullmarn, 3 sps (Loven 1871); D:o many sps (Ärnbäck, July 

 1918); Flatholmen, 1 sp (July 14, 1876, C. Bovallius); Kristineberg, 1 sp (1893); 

 Pittlehufvud, 30 — 35 m, mud, 3 sps; Humlesäcken, 60 fms, 2 sps; Gåsö, Fittebojen, 

 25 fms, 1 sp (July 4, 1876 Mus. G.); Gåsö skären, 14 fms, 3 sps (August 10, 1881 

 Mus. G.). — Väderöarna, 10—60 fms, rocks and corals, many sps (1862). — Koster, 

 1 sp (1869 Bovallius); Kosterrännan, 25 fms, 1 sp (July 18, 1877); Kosterf jorden, 

 3 sp (June 1895, C. Aurivillius). — Dyngö, 8 fms, 2 sps rocks. — Skåne: Kullen, 

 3 sps (Loven); Landskrona— Malmö, 6 — 9 fms, blue-clay, stones and algae, 1 sp 

 (July 22, 1878, Gunhild Exp. Théel & Trybom); Grytskärspricken — Skaudden, 10 

 fms, Zostera, 2 sps (July 19, 1902, E. Lönnberg). 



Baltic sea: W. of Bornholm 55° 10',ö N— 14° 13' E, 27 fms, sand with clay, 

 1 sp (July 31, 1878, Gunhild Exp. Théel & Trybom). 



