134 



Jorge 



der pointed branches (spines), more or less distinctly scattered in com- 

 parison to those on the other edges of the same spine, only rarely 

 here and there in distinct verticils. 



Between the neighbouring branches of the different main spines, 

 rather long and tine connecting beams extend, these being in their 

 turn again connected by numerous similar ones. Thus a more or 

 less perfect net is formed which is best developed between the 

 apical spine (D) and the ventral, sagittal one. This network forms 

 a rather imperfect lattice shell with meshes, very uneven in shape 

 and size, fi'om small, triangular and trapezoidal to very large, po- 

 lygonal openings. Also the inner branches (spines) on the same 

 main spine are connected, partly with the main spine itself, partly 

 ■i\'ith each other, also by line connecting beams, parallel to the di- 

 rection of the main spine (as in the spines of Rhizoplegma hureale). 



The meshes of the lattice shell strongly recall those of Cla- 

 doscenmm tricolpium. Very often (in young individuals) so little 

 of the network is developed that it would not be justifiable to 

 consider the species as a Euscenium, if one did not occasionally 

 tind a well developed latiee shell. Cfr. Joegensen 1. c. 



This species is very different from Cladoseenium tricolpium, 

 and without doubt is more closely allied to those forms which have 

 an imperfect lattice shell (Plectoidea Hck.). It might be classed 

 as belonging to the genus Periplecta Hck., if it were not for the 

 distinct, ventral, sagittal spine. (This spine was previously over- 

 looked, and for this reason is not mentioned in my earlier description 

 of the species 1. c. p. 77). I prefer at pi'esent to let it remain 

 in the genus Eu.icenium, rather than to start a new genus, as the 

 genus Eiixceiimm Hck. certainly requires revision. 



Cladoiiseeninin tricolpium (Hck.) JfiRa. 

 (PI. XV, figs. 71—73). 



Euscenium tricolpium Hck. L. 86, p. 1147, pi. 5:3, f. 12. 

 Cladoseenium tricolpium, Jokg. L. 91, p. 78. 



Here again we have the four primary spines and tlio ventral 

 sagittal one. The almost central columella corresponds to the 

 basal, dorsal spine, D, in Plectacantha oiMskos and Phormacantha 

 lujstrix. On the other hand, the connection with Protoseenium 

 simplex is evident. 



From two, somewhat ui)wards ixtintiug, branches from each of 

 tlic left and right lateral spine four arches extend upwards and 

 miite in twos (those from the same main spine) to form a strong 

 ai)ical arch. These are the corresponding arches in Protoseenium 

 simplex, where they connect the branches of the lateral spines with 

 the corresponding two branches of the apical one (D). The tips 

 of these branches have disappeared in Cladoseenium, and the arches 

 pass gradually into the branches. The two corresponding ones in 

 tlie dorsal spine (A) are also found; but one of them is not parti- 

 cularly conspicuous as there are several similar secondary arches. 



The lattice shell (cfr. .Torgensex 1. c. p. 78) is particularly 

 pci'fect between the apical spine (D) and the ventral, sagittal one. 



There are, where the main spines protrude, I'atiier large, tri- 

 angular meshes formed by connecting beams between the larger 

 arches of the shell and the spines, two at the dorsal spine (A) and 

 the left, lateral spine (L,, ). three at tiie apical spine (D). It is 



only in older individuals that tlic lonir, line downhanging spines are 

 formed on the basal arches (i. e. tlic arches between the basal 

 spines. A, \j and Lj^ 



There does not seem to be anything of impoi'tance to prevent 

 us from considering this species to be identical to Euscenium tri- 

 colpium Hck. It is true that, in Haeckel's illustration, the distinct, 

 ventral, sagittal spine is not present. There are, however, so many 

 details in the illustration, which answer remarkably well to this 

 species that it is highly probable that they are identical. The 

 reason why Haeckel refers the species to the genus Euscenium, 

 is that he considers the shell to be closed by the strong apical 

 ai'ches, (which are conspicuous in certain sightings of the microscope) 

 while it really extends farther up along the apical spine, to the three 

 connecting beams above mentioned. 



My opinion therefore is still that the species is a Cladoseenium. 

 Haeckel mentions the completely corresponding upper arches in 

 Cladoseenium peetinatum Hck. (L. 86, p. 11.50, pi. 98, f. 2), as a 

 second verticil of branches of the columella. 



Frequent, always in small numbers, in deep water, up to 

 100 m. 



Distribution: Not rare on the west coast of Norway, here too 

 sparse, and only in deep water samples. Was found in surface 

 samples from the warmer and salter Atlantic waters V2 1901, in 

 the sea beyond Søndmøre, 'V2 off" Lofoten and Vs off Finmarken 

 (cfr. Gran L. 70, pp. 150, 151, 154). Mentioned by Haeckel from 

 a great depth in the Central Pacific. Cleve has found the species 

 at a great depth west of Spitzbergen and at some places in the 

 northern and north western parts of the Atlantic. Cleve (L. 40, 

 p. 161) remarks that the species, though often found together with 

 Styliplankton (tempei'ate oceanic), does not, however, appear to be a 

 Btyliplankton form. Cleve considers it likely, either that it comes 

 from the northern polar basin, or from the Northern Pacific. Cfr. 

 above, p. 128. 



Cladosceniinii liuibatiiiu Jørg. 11. sp. 

 (Pl. XV, fig. 74.) 



Resembles to some extent the foregoing species, and is, on the 

 whole, of the same structure, but, is nevertheless, quite different 

 through the following special characteristics: 



The main spines are more broadly three-edged, each edge 

 having 2 to 4 diverging spines, which nearest to the shell are often 

 prolongated to arch-shaped fine, supporting branches, between the 

 shell and the main spine. Such arches are only seen from the one 

 or two innermost branches (spines) and most clearly on the upper 

 side of the main spines. Outside the basal arches, perhaps only 

 between the lateral spines, a brim-shaped continuation of the lattice 

 shell is developed. This bi'im continues a little way foi'wards along 

 the sides of the main spines. 



There is a verticil of branches high up on the columella, as 

 in the foregoing species, but these branches are here almost straiglit 

 on the distance between the columella and the shell. 



The network of the lattice shell is much more perfect than in 

 the foregoing species, mo.st of the meshes being small and more 

 or less distinctly square. 



There is a trace of lattice wiims from the top liorn to the 

 basal spines, and for this reason the species, perhaps, should most 

 correctly be referred to the genus Pteroseenium- Hck. 



The cephalis is 52 \>. in height, the width between the lateral 

 spines 56 [j.. The right, lateral spine is 68 \i. in length outside the 

 shell, the tophorn 50 jj.. The stronger, primary arches seem here 

 to become less conspicuous with growing age, so as to make the 

 network more even in development. Finally the pores seem to dis- 



