572 



I am inclined to think that E. Jorgensen is right in sepa- 

 rating the forms named »C. criophilum«, into two species, viz. 

 C. convolutam Castr. and C. criophilum Castr. 



None of them are common aronnd the Færoes. 



The true C. convolulum occurred only in a few specimens in March 

 and May— September. 



34. C. criophilum Castr., Challenger Rep., 1886, p. 78, with tig.; 

 C. periwianum Vanhoffen, Gronl. Expedition d. Gesellseh. fur Erd- 

 kunde zu Berlin, 1897, Bd. II, 1, PI. 3, figs. 5-7; non Brightwell. 



As rare as the above species, found in March, April. Both species 

 are boreal, oceanic. 



Note. To this section we mav also refer the following species: — C. peruvianum 

 Btw. (= C. volans Schiitt, C. curiens Cleve), C. rudis Cleve, C. densum Cleve, 

 C. robustum Cleve, C. curvalum Castr., C. sallans Cleve, C. coarctatum Laud., C. den- 

 ticulatum Laud., C. roslralum Laud., C. aequaloriale Cleve, C. danicuni Cleve, C. te- 

 irastichon Cleve, C. Aurivillii Cleve and perhaps C. radiculiun Castr. 



Subgen. 2, HYALOCHAETE Gran. 

 Sectio 1. Oceanicae. Chromatophores rather large, 4 — 10; awns 

 coalesced along a short portion of their length: no endocysts. 



35. C. decipiens Cleve, Arctic Sea, 1873, p. 11, PI. I, fig. 5 a, b. 



Common in the plankton from the Færoes, found all the year round, 

 predominant in many samples from March to August and especially in 

 April— May. It is a boreal, oceanic species, the optimum temperature of 

 which here is 7°— 10° C. [See tables]. 



Note. Perhaps C. femur Schiitt and C. fusus Schiitt helong to this section. 



Sectio 2. Cylindricae. Chromatophores small, numerous; cells 

 terete (valve circular); foramina very narrow; terminal awns not 

 thicker than the others; endocysts somewhere about the middle of 

 the cells, smooth or with spines. 



36. C. teres Cleve, Bih. Sv. Vet. Akad. Handl., Bd. 22, 3, No. 5, 

 1886, p. 30, fig. 7. 



A boreal-arctic, ncritic species, which is ralher common from March — 

 June, sparingly in the other months; found with endocysts in April and 

 May. Optimum of temperature 7°— 9° C. [See tables. i 



Note. To this section helong C. Weissflogii Schiitt, C. Schmidtii Ostf. , and 

 perhaps (1. Lauderi Halls. 



Sectio 3. Constriclae. Chromatophores one or two; cells more 

 or less constricted; hoop at least 1 /a of the length of the cell; ter- 

 minal awns mostlv thicker thah the others; endocysts, in the species 

 where they are found, somewhere about the middle of the cell, and 

 with numerous spines on both valves. 



