OSCAR SUND 



(REP. OF THE "MICHAEL SARS" NORTH 



Table of sizes. (C in mm.) 



Size 



IV2 



2 



2 l /2 



3 



3'/2 



4 



5 



6 



7 







Males 















7 



5 



3 



Females .. 















5 



15 



7 



Young ... i 

 Indet 1 



3 



22 



1 



18 



3 



16 



10 



6 



4 



In this species, the length of 

 the carapace (C) seems not to ex- 

 ceed 7 mm. corresponding to a total 

 length of about 20 mm. A figure 

 is given of the petasma (fig. 4). 



Fig. 4. S. atlanticus, 



<? 7, st. 48, 1/2 sn 7800, 



petasma, ( 15 A). 



Tab U 



' of catches. 



(Hauls made during night marked * ) 





St. 



Gear m. v. 



Number 



Sex, size 





19 



4 In 



900 



1 



© 2 





25* 



V2 sn 



3400 



1 



? 6 





29 



y 



400 



5 



2 7, d" 6, 5, 5, 5 





■ 



y 



2000 



2 



? 6, d* 7 





34* 



y 



400 



1 



? 7 





42* 



y 



900 



1 



2 6 





45* 



1 sn 



200 



2 



© 3, 3 





:£ 



y 



300 



3 



? (?) 7, 6, 6 





* 



y 



2000 



2 



2 7, 7 





48 



1 sn 







1 



©4 





B 



V2 sn 



7800 



1 



cf 7 





49* 



y 



2000 



1 



©3 





51* 



1 sn 







4 



^ 7, © 3, 3, 2 





52 



1 sn 







15 



7, 7, 7, 6, 6, 6, 6, 5, 5, 5, 5, 4, 

 1V« 



4, 2 



• 



V2 sn 



100 



1 



© IV2 (dubious) 





s 



3 sn 



1200 



1 



7 





53* 



1 sn 







9 



6, 5, 5, 5, 5, 4, 4, 4, 3 





* 



1 sn 



100 



11 



2 6, 6, d» 6, 6, 6, 5, 5, 5, © 3Va, 



IV2 



* 



y 



300 



2 



2 6, 6 





* 



y 



1600 



1 



©3 





£ 



3 In 



2600 



2 



2 6, 5 





56* 



1 sn 







2 



© 3Vs, 3V 2 





* 



1 sn 



100 



1 



©3 







y 



2000 



1 



©4 





* 



3 In 



3000 



2 



2 7, 6 





62* 



1 sn 







2 



3 4, 2V2 





64 



1 sn 



200 



11 



© 4, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2 





a 



y 



300 



15 



© 4, 4, 4, 3, 3, 3, 3, 3, 2, 2, 2, 2, 2 



2,2 



» 



3 A sn 



600 



1 



©2 





* 



y 



1000 



2 



© 5, 4, 2 





» 



y 



2000 



4 



6, 5, 5, 3 





» 



3 /i sn 



2500 



3 



2 5, d" 6, 5 





67 



y 



200 



5 



© 4, 3, 3, 3, 3 





* 



y 



1200 



6 



2 7, 6, 6, 6, © 4, 4 





69 



1 sn 



200 



1 



©2 





80 



3 U sn 



600 



2 



3 5, 5 





17 



36 





125 





-n 



Sergestes arct/cus Kroyer. 

 S. arcticus, Kroyer 1855. 

 S. atlanticus, Bate 1888 (partin). 

 5. arcticus, Hansen 1906. 

 5. arcticus, Wasserloos 1908. 



This species seems to bee 

 commonest of the genus, and 

 was indeed captured by the 

 "Michael Sars" Expedition in all 

 regions of the North Atlantic. 

 Its anatomy is so well known 

 that it is unnecessary to add 

 anything but a drawing of the 

 petasma (fig. 5), to show the 

 homologies with S. robustus, the 

 petasma of which I have taken 

 as the standard of comparison 

 (see fig. 11). It will be seen that 

 the part d is not found in S. 

 arcticus, while the part c, which 

 in most species is unarmed, is 

 in this species armed with a row 

 of spine clusters. This structure is figured by Kemp 

 (1910) pi. III. 



The "Michael Sars" specimens are arranged according 

 to size in the following table: 



Fig. 5. S. arcticus, cT 16, st. 

 102, 3 In 1500, Petasma, ( 13 /i). 





Sizes (C in mm.) 





1 |2 



3 



4 



5 



6 



7 



8 



9 



10 



11 



12 



13 



14 



15 



16 



17 



18 



19 



Males 



18 



23 



2 



8 



19 



26 



20 



6 



9 



1 



2 



3 

 2 



5 

 2 



1 

 4 



5 



1 

 5 



4 



3 





Females 



9 



Young 









The vertical distribution differs for the larvas and for 

 the adults, and is correlated with the fact that the latter 

 posses a fair amount of red pigment (see Kemp 1910, 

 p. 32), while the larvae are nearly colourless. (Compare 

 this with the table of vertical distribution of the different 

 sizes). 



Depth m. 



Hauls 



Size (C in mm.) 



Total 



1—9 



10—15 



16—19 





0—200 

 201—500 

 over 500 



12 

 14 

 17 



55 

 48 

 27 



1 



5 



18 



15 



56 

 53 

 60 



Total 



44 1) 



100 



24 



15 



170 



It appears that the grown up individuals do not 

 ascend much beyond 500 m. from the surface, the species 

 resembling in this respect Acantephyra purpurea and other 

 prawns, the horizontal distribution of which it also shares, 

 being found all over the Atlantic, as far north as 65° N. lat. 

 between Iceland and Greenland. It has also been taken 

 in the Norwegian Sea on several occasions both by Danish 



1) One haul from unknown depth. 



