llfi 



E. Joi'oensen. 



ces whei'G the .sea water lias easy access. During- the spring 

 diatom inflow, it seems generally to be absent, except at greater 

 depths in the inner fiords, where scattered specimens occur. This 

 also seems to be the case, on the whole, with regard to the other 

 SpKinelhtria. 



Disfrihntio'ii : Chiefly the same as in the preceding species, often 

 toiicther with it. 



VII A. 2. Aiiitrofiipliærida H( ic. 



Krliinoniiiia leptoderiuiiui Jokg. 

 (PI. VIII, r. :«). 



.JOEGENSEN L. 91, p. 57. 



This species is at once recognized by having more numerous 

 and shorter radial spines, larger and more uneven pores on its out- 

 side .shell, as well as by its irregular (deformed) middle shell. It 

 is also in other respects very ditt'erent from the two preceding 

 species. 



The outer ball thinwalled (the walls broader than they are 

 thick). The pores polygqnally roundish oval, very uneven in size, 

 7— 25 |i, with intermediate walls (2— i |j. broad)-, which arc much 

 broader towards the corners (lumen rounded off). 



The middle shell moderately thick (the intermediate walls being as 

 thick as they are wide, about 1 ^'2 i)-), rather angular and irregular, 

 a little larger than in Hexaconfium enthacanthum ; diameter about 

 40 |).. The pores somewhat uneven, roundish, 4 — 7 |j.. The inter- 

 mediate walls solid, not particularly broader in the corners. 



It is difficult to see the inmost shell, which possesses solid 

 beams (about equal in thickness to those of the middle .shell), but 

 rather few polygonal, mostly pentagonal or hexagonal pores, about 

 8 ]>.. The diameter of the inmost shell about 15 \>- (or a little more). 



About 15 main spines, about equally broad inside as outside 

 of the outmost shell, not long. They seldom protrude farther than 

 to a length equal to the distance between the two outer shells, 

 often less, and vary in development. Between the two inner shells, 

 the radial spines arc very narrow and in fact hardly widei- than 

 the beams of the inmost shell. 



The byspines on the outside shell are in appearance like the 

 main spines, but not radially lengthened inwards, with a wide base 

 oil the outer shell (like the main spines) and very unevenly devel- 

 oped in size, although generally protruding less than the main spines. 

 Variable in number; although, as a rule, not many, far from being 

 devcdoped in all the corners, only here and there. 



The number of the main spines is variable, often only about 

 10, though oftene.st about 15. They are .3-edged as in if r.x« (■•«/(/»;;/ 

 purhijdfnii 11)11. 



The nearest relation to this .species is, without doubt, K. Irin- 

 acri/nii Hck., which .species, however, to Judue from Hæckel's illu- 

 stration and description ■ (L. 84, p. 441, pi. 24, f. 6-— 8) is well 

 distinguished by the construction of the inside ball, as well as by 

 several other, less important, characteristics (as the number of the 

 pores and spines). 



As in HcxnconfuDii juirln/ilrniuiiH and //. ciillKinnillniui. tliei'e 

 are forms without outer shells, but thi.'i'e is generally a trace of 

 these in transverse processus on the main spines. These may, hoA\- 

 evei', also be entirely absent. Such forms, of which one is illu- 

 strated on pi. VIII f. .33 c, might equally well he i-eckoned as 

 belonging to the genus Aclinommit (without bvsiiines on the third 



shell), respectively Haliommn (with only two shells), if their di- 

 mensions and other characteristics were not completely correspond- 

 ing to the above species. Cfr. Jobgensen 1. c. p. 58. 



This .species also varies a good deal. When the outside shell 

 is thin-walled, the pores and intermediate walls are of a more 

 uneven size. The by.spines are in such cases slightly developed or 

 (as yet) wanting. 



It is likely that these divergences may be accounted for by a 

 difterence in age. A moi'e important difference is the number of 

 main spines, which seems to be able to vary from 10 to 16. 



Comparatively frequent, though, like all radiolaria with us, 

 always present in small numbers. It occurs, however, decidedly 

 more frequently and in larger numbers than the two Hcxacontiam 

 species. 



DisirihiifKiii : The same as that of Hr.iuconlinm enthacanthum 

 and H. parliyilciinau/. Frequent also on the west coast of Norway 

 and in the Norwegian 8ea. 



E. trinacrium Hck. 



The forms which I have tabulated under this name are some- 

 what uncertain. They are distinguished from the foregoing species 

 by a strong, rather thick outer shell, more numerous and stronger 

 byspines, as well as by a different construction of the inmost shell, 

 which is in most respects like the middle one. 



There is nevertheless on the one side a considerable agreement 

 with Chromyechinus horcnlis, only that the outside shell (the fourth) 

 is wanting, on the other side a considerable resemblance to younger 

 forms of Drymyomma elegans, where the characteristic branched 

 byspines are still wanting or are branchless needles. To this must 

 be added that different forms of E. leptodermum may also have rather 

 strong outer shells and more numerous spines. 



As a rule, though, the forms of Cliromyccliinu.^ horealix may 

 easily be recognized by the transverse processus on the radial spi- 

 nes, which here, as in E. Icptodermum and Hexacontimn enthacanttnnn 

 suggest the beginnings of the still undeveloped outer shell. The 

 forms of Drymyomma elegans have characteristic long slendei- main 

 spines and narrow byspines. Yet, I am not sure if there be not 

 still another species, most nearly answering to E. trinacriuvi, but 

 with long, narrow principal spines and byspines. the latter always 

 being branchless. 



It is difficult to examine the imnost shell. I have not yet 

 succeeded in ascertaining with certainty whether such a firmly con- 

 structed inner shell with which E. trinacrium is depicted by 

 Haeckel (L. 84, pi. 24, f. (>— 81 is also characteristic of Chro- 

 myechinus horealis and Uryiiiijiiiiinia (d'ljmis. T have, howev'cr, seen 

 such a .shell. 



As 1 have already suggested in a jircvions paper (.lnudioxsKN 

 L. 91, p. 57) it is not impossible that what I have called E. tri- 

 nacriuiii may be certain young forms of Chromyechinus horealis, 

 whci-e the above mentioned transverse processus on the radial 

 spines are wanting. On the other hand, it is just as likely that 

 there may bo with us another species differing from both Drymy- 

 omma elegans and Echinommn trinacrium, to which the supposed 

 intermediate forms belong. This species would be coinparativcly 

 frequent on the northern coasts of Norway. 



I'ntil this is made evident, it will be best to keeji to the spe- 

 cies which arc always ea,sily recognized, viz. Echinommn leploili'r- 

 mum, Chniiiiycchiiiiis horealis and Drymyomma elegans. 



Occin's in the plankton like the foi'egoing species. 



