31 



preservation being not as good as desirable, il is impossible lo ascertain 

 whellier there are large pigment spots at the point of I be long arms, as 

 is the case in the larva- of .1. li.iulti and puncliildld. The vibralile lobes 

 are not yet developed, but there is no reason to doubt that they will be 

 found here as in the other Arbdciu-\arvse. 



The skeleton (Fig. 5) agrees very closely with that of the . 1. li.ruln- 

 larva (comp. .Job. Miiller, VII. Abb., Taf. II, Fig. 10), especially in the 

 noteworthy feature that the posloral rods are feneslrated only in the 

 point. Only the posterior transverse rod dillers from that of the .1. li.rulti- 

 larva in being somewhat curved and more robust, more like that of the 

 .1. punctuldta-lSLTva, which, on the other hand, dill'ers from the present 

 larva and A. li.niln in having the posloral rods fenesl rated from the base. 



In a plankton sample from oil the A/ores (3613' X. 33 .">()' \V., lo/III 

 1011), taken onboard the "Ingolf" by Mr. II. Blegvad, was found an 

 Arbaciid larva which is remarkable on account of its exceedingly long 

 postero-laleral arms (PI. VI, Figs. 1 2). The shape of the body cannot 

 be made out clearly on account of the rather advanced stage of meta- 

 morphosis, likewise the vibralile lobes cannot be distinguished. The 

 preoral lobe evidently is somewhat altered by the beginning absorption: 

 il has the appearance that the vibralile band passes all round its edge, 

 which cannot be a normal feature in the larva. The structure of the post- 

 oral and posterodorsal rods is like that in the .1. li.rnld larva (both these 

 pairs of arms are broken, so thai their full length cannot be ascertained). 

 The posterolateral rods are sparsely thorny, the thorns beginning a little 

 outside the part lhat is represented in PI. VI, Fig. 2. The posterior 

 transverse rod is slightly curved, with no distinct hole in the middle. 



It seems hardly possible that this larva might belong to .1. li.iuln: 

 the posterior transverse rod is different and even in the more advanced 

 stages of metamorphosis the larva of that species has never been observed 

 lo possess such exceedingly long posterolateral arms 1 ). There is then 

 reason lo suppose lhat this larva belongs to one of the other species of 

 the genus Arbddn (A. afrit-diid:'), or perhaps to Arbddclld eleydm. There 

 is also a possibility that il may belong to a deep-sea form (('.aclo/tlt'iinis 

 or Podocidaris); at least such possibility cannot- be rejected beforehand, 

 so long as nothing is known regarding the character of the eggs in these 

 deep-sea forms. Anyhow, il has seemed lo me worth while calling alien- 

 lion to this conspicuous larval form. 



M .loh. Miiller. VII. Abhaiulhmg. Tal. II -III. I., v. rbisch. Die Anlatfc mid Aus- 

 bildung cles Skelet systems i-imger Kcbiniden, und die Symmetrieverbftltnisse von I.arvr mid 

 Imago. Zeitsclir. wiss. /ool. CIV. HUH. Tal. VII. 



