ATLANT. DEEP-SEA EXPED. 1910. VOL. III.] 



PFNEIDES AND STENOPIDES. 



11 



appears that the species mostly lives in the intermediate 

 waterlayers, and rises some hundred metres nearer to the 

 surface during the dark hours. 



Table of vertical distribution. 



Depth 

 (metres) 





Size (C in mm.) 











3—10 



11—19 







D 



N 



D 



N 



D 



N 



D 



N 





0—100 

 150—200 

 300—1700 



1 

 1 



4 



5 

 7 

 6 



2 

 1 

 4 



7 

 1 

 2 



1 



2 



6 

 22 



7 



2 

 2 

 6 



13 



23 



9 



15 

 25 

 15 



Total 



9 



18 



7 10 



3 



35 



10 



45 



55 1) 



Gr. tot. . . 



27 



17 



38 



551) 





Table of catches. (Hauls during night marked * ) 



St. 



Gear 



m. w. 



Number 



Sex, size 



23* 



1 sn 



200 



2 



? 16, d" 13 





» " 



y 



400 



3 



5 17, 16, cT 17 





25 



V2 sn 



3400 



1 



©10 





29 



y 



400 



2 



S 12, ©9 





34* 



y 



400 



1 



5 16 





45* 



y 



300 



2 



©9, 11 





49* 



4 In 



1000-0 



2 



$ 17, 17 (verticai haul) 





B ! 



4 In 



3000 



2 



$ 19, 17 





51* 



1 sn 



200 



1 



?15, 





* 



y 



300 



6 



? 17, 16, 15, 14, J" 17, 15 





* 



y 



2000 



1 



2 18 





52 



y 



600 



1 



c? 14 





„ 



3 In 



1200 



1 



©7 





53* 



1 sn 



100 



4 



© 10, 8, 8. 4 





n 



1 sn 



200 



2 



© 10, 8 





n ' 



y 



300 



6 



2 17, 16, 16, 15, 14, d» 15 







3 In 



2600 



2 



? 18. ©8 





56* 



y 



300 



1 



? 18 





»'' 



3 In 



3000 



2 



$ 17, 15 





58* 



y 



300 



7 



? 16, 15, 13, 13, 13, cj" 17, 



12 



62* 



1 sn 







1 



© 4.2 (mast.) 





„ ' : ' 



y 



2000 



1 



©7 





n : " 



3 In 



3000 



1 



¥ 15 





64 



1 sn 



100 



1 



© 3.0 (mast.) 





„ 



1 sn 



600 



2 



©4, 4 





» 



3 In 



3000 



1 



©9 





67 



y 



200 



1 



©4.0 





88 



y 



1000 



1 



5 18 





15 



27 





57 



8a", 31 ?, 18© 















') Two specimens from vertical haul not considered. 



Sergestes robustus Smith 1882. 



5. dissimilis, Bate 1888. 

 5. mediterraneus, HANSEN 1896. 

 5. dissimilis, HANSEN 1903(1, 2). 

 S. inermis, Hansen 1903(2). 

 5. robustus, Hansen 1908. 

 — „— Kemp. 1910. 



Small individuals of this species were caught at nearly 

 all the stations during the expedition, as well as a few 

 fine adult specimens. The identification of this species 

 proved to be very easy from Smith's description, especially 

 as he has given a good drawing of the petasma, that 

 appendage which should be used as the "ear-mark" in 

 the genus Sergestes. Several doubtful species are in my 

 opinion rendered „good" on the evidence furnished by 

 the petasma. I have tried to use Smith's designations of 

 the different parts of this appendage when dealing with 

 other species, but in many cases the homology is rather 

 doubtful, especially in very distantly related species, for 

 instance 5". robustus and S. pectinatus. 



For the sake of a clearer understanding of the 

 petasma 1 reproduce here Smith's drawing (fig. 11) and 

 an additional figure of the outer portion, seen from 

 behind, Smith's figure being seen from before. The 

 "fingers" / and g seen from before look like separate 

 members, but in fact form one piece, bent in two planes 

 (see fig. 12). 



The smallest individual in which I could detect a 

 petasma was only 23 mm long (C = 7), and among the 

 individuals of C = 8 I found three with petasma buds. 

 Fig. 13 is drawn from a male of this size. There were 

 twelve individuals with C = 8, in wich no petasma could 

 be seen, but I dare not conclude that they are all females. 

 When C excedes 9 I believe than the petasma should be 

 easily seen, and I have therefore classed as females all 

 the specimens above 9 mm (C) without petasma. The 

 only adult female specimen is very like the male in 

 appearance, except that the eyes are slightly smaller. 



I cannot dismiss this opportunity of mentioning what 

 I believe to be the luminous organs of Sergestes robustus. 

 The structures in question are small opaque patches on 

 the scaphocerite and on the outer uropods, arranged in 

 a similar manner to that found in S. challenged. S. glo- 

 rious and 5. splendens. In 6". robustus there is a row 

 of 14 patches on the scaphocerite: 7 along the outer edge 

 of the muscle and 7 beyond the termination of it. On 

 the outer uropod there are 12 patches, six situated in 

 an irregular longitudinal row beyond the muscle, and 

 six near the inner setose edge, in a row occupying 

 the second fourth from the base of that edge. I have not 

 been able to find such patches on other parts of the body 



