34 



JAMES A. GRIEG 



[REP. OF THE "iMICHAEL" SARS NORTH 



■s/; stat. 35, 27°27'N. 14° 52' W., 2603 m., yellow mud. Arm 

 fragments. 



8 /e stat. 53, 34° 59' N. 33° 1' W., 2615—2865 m., yellow hard 

 clayey mud., temp. 3° Cel. One specimen. 



30/6 stat. 70, 42° 59' N. 51° 15' W., 1100 m., temp. 3.7 Cel. 

 Common. 



27 /t stat. 95, 50° 22' N. 11°44'W., 1797 m., temp. 3.5 C Cel. 

 Common. 



6/ 8 _7/ 8 s tat. 101, 57° 41' N. 11° 48' W., 1853 m., hard clay, temp. 

 3.3 1 Cel. Very common. 



Disc-diameter of the smallest specimens 2 mm., of 

 the largest 33 mm. In the smallest specimens with a 

 disc-diameter of 2 to 3 mm. (pi. 5, fig. 8) the dorsal side 

 of the disc consists of the central plate, the five primary- 

 plates, the radial shields and two small plates placed 

 interradially between the latter. By a disc-diameter of 4 

 mm. (pi. 5, fig. 9) a secondary plate between the primary 

 plates and the radial shields is added to the disc, which 

 thus possesses 31 plates. By a disc-diameter of 5 mm. 

 (pi. 5, fig 10) this number is further increased by 5 se- 

 condary plates situated interradially between the primary 

 plates, and the number goes on increasing rapidly with 

 continued growth of the disc. The central plates with 

 secondary plates becomes separated from the primary 

 plates, and these from the radial shields, and so on. 



Mortensen has shown in "Smaa faunistiske og bio- 

 logiske Meddelelser" x ) that ophiurids of various ages are 

 found simultaneously in shallow water at the same 

 locality within the boreal region, and that recently trans- 

 formed young were collected at the same time with 

 one-year old, fully developed two-year old and older 

 individuals. In Arctic waters on the other hand only a 

 single year-class as a rule is found of the ophiurids 

 occurring at locality. A few year-classes may, however, 

 as an exception occur simultaneously, cfr. Mortensen: 

 Echinoderms from East Greenland'-) and Grieg: „Michaei 

 Sars Ophiuroidea" 



Among the ophiurids collected by the "Michael Sars" 

 in 1910 in the North Atlantic Ophiomusium lymani 

 only was represented by a greater number of specimens. 

 In the following synoptic table the measurements of their 

 disc-diameter will be given. As will be seen from 

 this table the great mass of the individuals at a locality 

 seem to belong to the same year-class. Two or three year- 

 classes may, however, occur at the same locality, pos- 

 sibly more. At stat. 25 A there was a maximum of 11 

 individuals with disc-diameter 15—17 mm., which no doubt 

 represented a year-class. Possibly one or two more year- 

 classes may be found at this station, but the material was 

 too scanty to determine this definitely. At stat. 25 B there 



') Vidensk. Meddelelser 1897, p. 321. 



2 ) Meddel. om Granland, vol. 29 1903, p. 82. 



3 ) Bergens Museums Aarbog 1903 no. 13, p. 23. 



was a maximum of 25 individuals with a disc-diameter of 

 18 — 19 mm. The 7 individuals with a disc-diameter of 12 

 — 13 mm. may possibly represent still another year-class. 

 Three year-classes at least occurred at stat. 70 where a 

 group of 30 individuals afforded a maximum at 23—25 

 mm., a small one of six individuals at 17 mm. and a great 

 one of 56 individuals at 4 — 7 mm. It is probable, however, 

 that the 3—5 mm. examples represented one year-class, 

 and that there was besides a fourth about 10 mm. At 

 stat. 95 a group of 19 individuals afforded a maximum 

 at 27 — 29 mm. Concerning the remaining 11 to 23 mm. 

 sizes no definite statement can be made, as only single 

 specimens of this group were to hand. They probably 

 represent at least one year-class, however. At stat. 101 

 there was a very marked maximum at 26 to 29 mm. 

 Besides, the smallest individuals must also represent one 

 year-class. Thus two year-classes at least are found in 

 that locality. 



Disc- 



Stat. 



Stat. 



Stat. 



Stat. 



Stat. 



Disc- 



Stat. 



Stat. 



Stat. 



Stat. 



Stat. 



dia- 



25 a 



25 b 



70 



95 



101 



dia- 



25 a 



25 b 



70 



95 



101 



meter 













meter 













in mm. 



Number of specimens 



in mm. 



Number of specimens 



2 







2 







19 



1 



13 



2 



1 



7 



3 







4 







20 



2 



7 



2 





4 



4 







17 







21 





10 



1 



1 



4 



5 







19 







22 



1 





1 



1 



5 



6 







9 







23 







8 



1 



4 



7 







11 







24 







13 





7 



8 













25 







9 



1 



16 



9 







3 







26 







3 



2 



24 



10 







5 







27 







1 



7 



30 



11 



1 





2 



1 





28 









7 



43 



12 





1 



2 







29 





























5 



24 



13 



1 



6 



1 



1 





























30 









2 



13 



14 



2 







1 



2 













15 



3 



5 



1 



1 



2 



31 









1 





16 



3 



10 



2 





2 



32 











4 



17 



5 



10 



6 



1 





33 











3 



18 



1 



12 



2 





1 





20 



81 



126 



34 



203 



As examples for comparison I may mention Pectinura 

 elata, Ophiura tessellata, Ophiocten sericeum and Ophia- 

 cantha abyssicola. At stat. 25 B 8 specimens of Pectinura 

 elata were taken. Seven of these had a disc-diameter of 

 21 — 25.5 mm., and one of 14 mm. The last-named indi- 

 vidual can hardly belong to the same year-class as the 

 rest. At stat. 88 15 specimens of Ophiura tesselata, (disc- 

 diameter 9 — 24 mm.) were obtained, which are grouped 

 as follows: There are three examples each of 24 mm., 

 21 mm. and 18 mm. Two specimens measured 20 mm. 

 The sizes 19, 16, 15 and 9 mm. are represented by only 



