]n| FESTSKRIFT FÖR LILLJEBORG 



well as the iris partly project through the palpebral opening. These openings 

 (the palpebral and that of the iris) are larger in our specimen than in the Challenger- 

 specimen, although the latter was itself much larger. This is however not a specific 

 characteristic. It only proves that these organs, the palpebral and the iris, are ca- 

 pable of considerable contraction and dilation. 



The olfactory organ has about the same situation as in Spirula peronii and 

 austrahs near the base and posterior margin of the ocular prominence "at the junction 

 ol the lateral and ventral faces of the head". It is easily seen and looks to the 

 naked eye like a whitish papilla on the otherwise strongly pigmented ground. 



The funnel projects in the emargination between the two ventral, anterior 

 lobes of the mantle. On the internal cephalic wall a rather broad valve can easily 

 be seen through the exterior opening. 



The mantle is entirely reticulated with small irregular pits or depressions just 

 as Owen, who was the first to observe them, described. These pits or depressions are 

 conspicuously larger round the shell-openings. The margins of the mantle round the 

 shell-openings are even, without any projections over the shell such as Spiru/a pe- 

 ronii is supposed to have. As Pelseneer has stated contra Owen and Steenstrup 

 the margins of the mantle are quite free from the periostracum which covers the shell. 



Pelseneer writes 1 , about the different layers of the mantle that, proceeding 

 from without inwards in addition to the epithelium and the chromatophores we find: 

 "first a layer of connective tissue, dense and glassy superficially, and looser below; 

 second a thin layer of longitudinal muscular fibres; third a thick layer with circular 

 muscular fibres traversed by radiating muscular bundles; fourth another thin layer of 

 longitudinal muscular fibres; and fifth the subcutaneous connective tissue of the inter- 

 nal face." The surface of the mantle of our specimen is (where only the epithelium 

 and the chromatophores are lost) white and of a silky appearance. These parts are 

 very loose and peel off in flakes. If these flakes are removed and put under the 

 microscope we find that the exterior part of them consists of connective tissue, the 

 interior of longitudinal muscular fibres. If the longitudinal muscular fibres are also 

 removed we strike, says Pelseneer, the third or central layer of circular muscles 

 which seems to be much more dense and compact than the others, but it is very 

 markedly pitted cud reticulated on the surface. 



The fibres of connective tissue resemble elastic fibres and arc wavy. A large 

 number of small roundish nuclei are seen in this tissue. Elliptical or approximately 

 round cellules with rather larger nuclei are also numerous and lie free in the con- 

 n. «tive tissue ; they may however possibly be blood-corpuscles. Here two nuclei are 



1 1. r. p. 7 . 



