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



PENEIDES AND STENOPIDES. 



21 



This table affords no evidence of a diurnal vertical 

 migration, like that found e. g. in the case of S. splen- 

 dens. A similar difference regarding this habit is found 

 in the peneid genus Amalopenceus, the large-eyed species 

 of which have a marked diurnal movement, while nothing 

 of that kind could be inferred from the data regarding 

 -the species which lives deepest and has the smallest 

 eyes, viz. A. Alicei. The same rule holds good in the 

 genus Sergestes, S. mollis having very small, 5. splen- 



Table of sizes. 



dens very large eyes. It will be noted that the large 

 specimens were all taken at a depth of 1000 metres or 

 deeper. 



S. mollis was formerly known only from deep water 

 along the Atlantic coast of the United States (Smith 84, 87). 

 During the "Michael Sars" Expedition it proved to be 

 fairly common, as it was taken nearly every time the 

 deep-sea plankton appliances were towed, even as far 

 north as between Scotland and Rockall (st. 101), but it has 



Size 



4 



5 



6 



7 



8 



9 



10 



11 



12 



13 



14 



15 



16 



17 



18 



19 



20 



21 



22 



23 



24 



25 



26 



Total 







Males 



1 



16 



16 



18 



7 



13 



12 



4 



7 



5 



3 

 2 



2 

 4 



2 

 4 



2 



4 



2 



1 

 3 



3 



1 





2 







1 



10 



Females 



Young 



26 

 99 



Table of catches. 



St. 



Gear 



m. w. 



Number 



Sex, size 



19 



4 In 



900 



1 



©5 



25 



V2sn 



3400 



2 



©10, 8 



29 



y 



2000 



2 



©10, 8 



35 



y h sn 



4200 



1 



©12 



42 



y 



900 



8 



©9, 7, 7, 7, 7. 6, 6, 6 



45 



y 



2000 



12 



$ 16, 16, ©11, 10,9,9,8,7,7,6,6,5 



n 



4 In 



3000 



5 



© 10, 9, 7, 7, 7 



49 



y 



2000 



6 



© 10, 10, 10, 9, 9, 7 



B 



4 In 



3000 



3 



© 9, 9, 7 



51 



x h sn 



700 



1 



©4 



„ 



y 



2000 



5 



c? 19, © 13, 8, 7, 5 



„ 



4 In 



4000 



2 



© 13, 7, 



53 



y 



1600 



2 



©12, 12 



B 



3 In 



2600 



12 



? 17, 15, d" 15, 14, © 12, 9, 9, 8, 7, 6, 5 



56 



y 



1000 



3 



© 5, 5, 5 



„ 



3 In 



3000 



1 



©8 



«2 



y 



1000 



2 



©6, 6 



„ 



y 



2000 



2 



011, 6 



„ 



3 In 



3000 



7 



? 23, © 13, 12, 10, 10, 10, 9 



•63 



4 sn 



4500- 

 15 00 



1 



? 18 



„ 



4 sn 



13 60- 

 45 



2 



2 17, ©10 



■64 



y 



2000 



13 



? 18, d" 15, © 13, 7, 7, 6, 6, 6, 5, 5, 

 5, 5, 5 





3 In 



3000 



9 



$ 20, 19, 19, 14, <? 17, 16, 14, © 12, 1 1 



66 



y 



1500 



1 



<^14 



67 



y 



1200 



9 



© 10, 8, 6, 6, 6, 6, 5, 5, 5 



80 



3 In 



3000 



3 



? 17, 15, 15 



81 



3 In 



3000 



7 



$ 23 (L = 71), 21 (L =64), 17, 16, 15, 14 



d* 17 



82 



y 



1000 



3 



©13, 12, 11 



84 



y 



1000 



1 



©5 



B 



3 In 



3000 



2 



? 20, 19 



87 



3 /i sn 



1500 



3 



© 12, 7, 5 



„ 



y 



2000 



1 



d"16 



92 



y 



3000 



1 



? 20 



101 



3 In 



2500 



2 



$ 26, 16 



22 



34 





135 





not been captured in the Norwegian Sea, where it prob- 

 ably does not occur, as we may infer from the non-occur- 

 rence there of other Atlantic deep-sea species, such as Hyme- 

 nodora gracilis Smith, which is indeed replaced in the 

 Norwegian Sea by a near relative: H. glacialis Bucholz. 



Sergestes vigilax Stimpson, H. I. Hanseu 



5. vigilax,, Stimpson 1860 (mastigopus). 

 S. vigilax, Hansen 1896. 



Hansen has described the adult very carefully, and 

 there can be no doubt as to the specific identity of Stimp- 

 son's young specimens and the adult described by Han- 

 sen. In the material from the "Michael Sars" expedition 

 all stages from the very smallest are present, and the 

 development of the charcteristic rostrum and maxilipeds 

 can be followed without interruption until they assume 

 their final shape, (see fig. 35 and 36). The number of 

 spines on the 6th joints of the maxillipeds I have found 

 to vary between 20 and 22, or rather less than stated by 

 Hansen (22 — 25). The 5th joint is subdivided into two 

 subjoints, the distal one being about one-fourth the length 

 of the entire joint. 



The petasma (fig. 38) is of quite another type from 

 that found in S. robustus, and shows the closest resemb- 

 lance to that of S. atlanticus. 



S. vigilax is a small species, as seen from the fol- 

 lowing table:— (specimens of 2V2 mm. are entered as 

 being 3 mm., etc.) 



Size (C. in mm.) 



1 



2 



3 1 4 



5 



6 



7 



8 



Total 



Males 



1 



39 



50 



26 



2 

 11 

 11 



13 

 20 



4 

 9 



2 



19 



Females 



42 



Young 



127 



