114 



E. Jørgenseu. 



as this organism is so minute, it cannot be expected that it should 

 be retained by the net. 



I have never succeeded in seing- anythins' but tlic siliceous 

 skeleton, notwithstanding that the species on our i\est coast docs 

 not seem to be so very rare. 



Distribution: Very imperfectly known. Cl. L. 40, p. 2hi) men- 

 tions it from Uvo places near tlie American coast. 



Wi««tepliann8 speculum (Ehkb.) Stohr. 



Generally speaking, rare and only singly; more frequent, 

 occasionally numerous, during the diatom inflow in spring. 



Is so small that it easily goes through the net. Its compara- 

 tive frequent occurrence during the diatom inflow may be partly 

 caused by its being retained by the diatom masses, but at any rate 

 plainly proves that at this period, it is of frequent occurrence in 

 the plankton. 



Dibtrihiitiun : Judging from its distribution, it appears to be 

 partly of southern origin, coming rather sparsely (?) to the 

 north Atlantic as a southern oceanic species, partly too of northern 

 origin, coming from the northern or arctic coasts. According to 

 Cleve, distributed over the temperate northern Atlantic; also known 

 from the English Channel (February and May 1903, occasionally 

 numerous), the North Sea, Skagerack, tlie Baltic, the west coast 

 of Norway, the sea between Norway and .Jan Mayen (in arctic 

 waters, frequent, cfr. Jokgensen L. 92, p. 36), Gi'eenland, .Tan 

 Mayen and the sea towards Spitzbergen. 



I>iof,vo«'lia fibula Ehkb. 



Cleve (L. 40, p. 154) considers it to be doubtful whether this 

 genus belongs to the SilieofldycJIatd or to the Eadiolaria. 



Rare and scarce. Occurs mostly in deep water samples. 



Distribution: Temperate oceanic form. Occurs in the Atlan- 

 tic, The English Channel, the North Sea, Skagerack, Cattegat, the 

 llultic and the west coast of Norwav. evervwiiere in small numbei's. 



Spherical shells, with several (more than 6) 

 main spines. 



3 sphei'ical shells, with broad 

 3-edged main spines and 

 similar or smaller simple by- 

 spines on the outer shell . . Echinommn. 



3 spherical shells, with nai-row 

 branching byspines on the 



outei' shell Dri/mi/onnna clcgcnis. 



4 spherical shells, with delicate 

 outer shell, which is pierced 

 by broad 3-edged main spines 

 and similar or smaller byspi- 

 nes from the next one Chromyechinxs boiralis. 



Spongy outer shell, which length- 

 ens out along the main spines 



as interwoven pyramids. . . . Rhizoph'iima horrale. 

 Circular discs, with porous plates above and 



below Stylodictya. 



Biconvex, spongy lens SiMngodiscus fxrus. 



Outer shell imperfectly closed, with con- 

 centric belts and large openings; inside, 



a double inner shell Phortioium jn/Ionium. 



Outer shell with broad porous plates, which 



coil themselves into a double spiral round 



an inner shell; numerous, long, naiTow. 



subulate spines Larcospira minor. 



Shell of irregular construction with strong, 



long protruding radial main spines 



(about 12) Streblacdntliri circitmterta. 



1. Ciibo!i«])liæri(la Hck. 



A'cry sparsely represented (unless one includes Blii^oplnium 

 Jiorcdiri. 



"VII. IEia,<a-±ola3r±a. 

 YII a. Si»iinieIIaria. 



'I'lie small number of species which have been observed all 

 belong to the deep water fauna, and usually occur rarely and sparsely. 

 'I'hcy all appi'ar to 1)0 contined to the warmer, salter Alantic wa- 

 ters, and are perhaps all of them temperate oceanic. As a rule^ 

 they are only found at places on the outer coast near the sea, 

 single specimens, however, have lieen found farthci- in at deep 

 places in the fiords, and these have probably been lii'ouglit in by 

 the water from the sea. 



During the period of the spring diatom iiitldw. they appear 

 to be absent except in the inner tiord dejitlis. where they may 

 still be found in a few .scattered specimens. 



Concerning the distribution cfr. farther below umler NasscUaria. 



Key to tlie genera of Spumellaria. 



Spherical shells, with (about) (j I'adial main spines in pairs pei'pendi- 



cular on each other Hcxacontitim. 



(Spongy outershell which length- 

 ens out as pyramidal scaftblds 

 along the main spines l-ihizoplcuwu borculc). 



j Hexaroiitinin entbacantum Jorg. and H. pacbydermmii Josn. 



.IOrgensen L. 91, p. 52—54, pi. II, f. 14. 



These species, which I at first thought very ditferent, agree so 

 remarkably in some respects, that now I consider it by no means 

 unlikely that B. enthacantlmm is a young state of H. puchydcrmuni. 

 The points of agreement are chiefly in the second shell and in all 

 probability also in the inner one, which is, however, more difficult 

 to examine carefully, as it cannot be seen well unless the outer 

 shells are removed. It is however difticult to obtain this without 

 destroying the inner shell. 



The points of disagreement are in the outer ball and ai-e so 

 evident in most instances that it will hardly be reconunendable, at 

 any rate at present, to consider the two species as identical. The 

 outermost shell does, nevertheless, appear to vary considerably, both 

 in diameter, the thickness of its wall and its pores, while the middle 

 one varies remarkably little. 



I have in exceptional cases found specimens of H. cntluicanthiiiu. 

 where there were signs, of byspines on the outermost shell (they 

 are easily broken ott'), but have however, never met with any in- 

 stance of doubt as to whether a given specimen was H. enthacun- 

 thim or H. pcichydermum, when only the outer shell was present. 



Whether there may possibly be several species or not, 1 have 

 not been able to decide, as both those above mentioned occur too 



