EINAR LÖNNBERG: NOTES ON SPIRULA RETICULATA OWEN 



1"1 



length, according to Owen's figure in Proc. Zool. Soc. 1880, Part II, PI XXXII 

 Fig. 1; and the female of the same species described by Owen in Ann & Mag Nat 

 Hist., ser. 5, Vol. Ill seems to have been just at slender. There is thus a remarkable 

 difference in shape between Spirula peronii and reticulata, on one side, and Spirula 

 australis on the other. 



The length of the exposed or externally visible part of the shell ex| 

 as a percentage of the dorsal length of the mantle is 



in Spirula peronii* dorsally 30 " ,, ventrally 



australis' „ 3I>9 n 23 



„ „ reticulata „ about 28 about 23, 



From this we see that the ventral shell-openings are, comparatively speaking, 

 almost equal in size in all three species, while the dorsal shell-opening is, compara- 

 tively speaking, much smaller in our specimen of Spirula reticulata than in Up 

 This depends upon the greater aboral development of the mantle in this specimen, 

 or, expressed otherwise, upon the somewhat large dorsal extension ol tin aboral 

 disk. This disk is smallest in Spirula australis. Pelseneer regarded it as b< 

 most developed in Spirula peronii, but we find that our specimen of Spirula retü it- 

 lata exceeds the two other species in this respect. This character is however pro- 

 bably subjected to individual changes with growth, as a large shell-opening is a ju- 

 venile character. So far as we hitherto know, Spirula australis is the most ancient 

 type in this respect, and the two others more advanced. It seems not impossibl« 

 that in very old individuals of these two species the shell-openings may be a g 

 deal more reduced, but it will hardly be quite closed. The- shape of the ventral 

 shell-opening is most like that of Spirula australis and reticulata in both of which 

 we find a furrow 3 separating the mantle from the terminal disk. 



The sessile arms are nearly subequal in length, but the dorsal pair i- tin 

 shortest, the second next, third and fourth a little longer, but of about the same 



1 According to Huxley's figure as cited above. 

 According to Owen's figure of the male specimen. There is ii" doubt dies 

 reliable and constructed with the utmost rare. 



3 In the above mentioned Blake-specimen from the West-Indii find th 



is probably the reason why Pelseneer, although with some hesitation, refers it to Spirula i 



think however that I shall be much mistaken if I suppose this Blake specimen to i 

 speries or at least a distinct variety which may provisionally be called Spirilla Hai 

 as follows. 1) Terminal disk separated by a furrow from the mantle. 2) Surface of mantl 

 well developed. 4) Tentacles much longer than head and bod)-. 5) Ventral arms 

 6) Shape of ventral shell-opening different (conf. figures). 7 1 Width of mantle nearly '/-' 

 stouter than .9. australis and nearly as thick as S. peronii). 8) iphical distribution: W 



Character 1) distinguishes it from S. peronii, 2) from reticulata, 3) from australis, 4), 5)8 



