ProtistplHiiktoii. 



appear. beiuL;- cldscd In" tliiii plates, so tliat tlicy are traiisl'ormed 

 into windows, not ojienini^s. 



( )nly tuc) speeiuK'ns oliserved: '■' , is;);), -lo miles NW of (ianlc- 

 vuTo. ()- -Tno ni. 



I*«>ri(liiiiii ll(K. 



Has the four primary spines as well as the ventral, sagittal one. 



I have i»rcviously (.IpiuiioNSEN L. 91, p. 75) expressed the 

 opinion that the L'enns Pcridiiim onght most naturally to be placed 

 npside (low n. with the ai'ehed dome (cephalis) downward.s and the 

 ojx'ninL;'. which is partly closed liy lattice work from the basal spines, 

 upwards. It is still my opinion that this is most correct aftci- the 

 analoary with Campylaeantha, Plectacnnilm and Plminacantha. Here 

 it may bo clearly proved that the apical spine in Haeckel's sense 

 ciiiiesponds to the dorsal, basal spine D in the genera mentioned. 

 \Nliile I, at the same time, considered the genera Euaccnium 

 and Cladoscenium to have apical netveork in contradistinction to 

 Pciidium and the group Pledoidea Hck. with a basal one, 1 have 

 later on come to the conclusion, after closer examination, that such 

 a dili'erence docs not exist. 1 have therefore retained Haeckel's 

 method of |)lacing so as not to bring Peridiiim in opposition to the 

 other genera of the group Ci/rtoidea Hck., for which 1 prefer from 

 practical reasons, at any rate foi- the present, to retain Haeckel's 

 method. 



P. longispinum Jørg. 

 (Pl. XV, fig». 75—79; pl. XVI. fig. 80.) 



Jørgensen L. 91, p. 75. 



I am for the pi'esent not quite sure whether or not there are 

 at lca.st two ditferent species included under this name. What makes 

 it still more difficult is that young forms of Dict/rtida often have 

 the appearance of a Peridhim, so that it is necessary to be very 

 careful in the determination. 



On older, well developed forms thei-e is a cephalis which is 

 broadest above the middle, then quickly rounded oti" upwards and 

 conically narrowed downwards. The lattice shell is well developed 

 and closed all round. The pores vary considerably in size, from 

 very small and round to large, oblong and polygonal. 



The main spines protrude far out. The very long and very 

 narrow points seem only to occur in younger individuals. Large 

 byspines, strongly bent outwards, are found on the right and left 

 lateral arches. Besides, there are smaller, straight byspines scattered 

 over all the surface of the shell, stronger and fewer in number at 

 the basal opening, numei-ous and tine, narrow, needle-shaped on the 

 upper side of the cephalis. 



Younger individuals (if these do belong to the same species) 

 with larger, more irregular pores, thinner beams, less perfectly 

 developed lattice shell and long and narrow main spines. The ce- 

 phalis in such forms is generally rounder, and often broader than 

 it is high. 



Here again we find the characteristic course of the primary 

 arches, as mentioned under Pledacantha oikiskos. The larger se- 

 condary meshes and spines, which are mentioned at the same place, 

 are also present here. 



Rather rare, in deep water samples, up to 50 m. 



Listrihiition : Also on the west coast of Norway, rare. Occurred 

 too in two surface samples from the warmer, salter Atlantic waters, 

 '/■■ 1901, otf Sondmore, and "A otf Lofoten (cfr. above, under Clado- 

 sceniitm tricolpimn). 



pi-esent, a- 



P. uiimitntn Ci,. 



Cleve L. ;!(), |). ;il, pi. .!. f. 1 a. b. c. 



The forms wliieli I have lelerred to this .species, occurred rarelx 

 in my n)ateiial. They may at once be distinguished from the pre- 

 ceding .species on account of the ab.sence of the muneious. fine 

 byspines on the u[)per part of the cephalis. 



VII C. 5. IMcyrtHla Hck. 



l/itlioiii4>lissa KiiRK. 

 The i'oin' piimaiT spines, A, I). L and 1 



well as the vcnti-al, sagittal one. 



The apical spine, D, runs in the wall of the cephalis, and 

 protrudes like a needle-shaped tophoin, the lower part being iaside 

 the lattice shell. The dorsal, basal .spine. A, protrudes obliquely 

 like a simple spike (needle), rather far down on the thorax. On the 

 inside, it is propped up against the shell by arch-shaped supporting 

 beams (corresponding to the apical arches in Plwrmacantha hi/strh-). 

 The lateral spines pierce the thorax in its upper part and protrude 

 each of them as (one or?) two spikes. 



The ventral, sagittal spine pi'otrudes near the region of the 

 neck (between cephalis and thorax), and is. in Lithomelissa setosa, 

 connected to the right lateral spine, Lj. l>y an inner, little lattice- 

 plate, whilst it is farther distant from the left, lateral spine. In 

 other words, it divides the angle between the lateral spines into 

 two very uneven paits, one small one to the right, and a larger 

 one to the left. By this feature, young forms of Lifhomelifsa se- 

 tosa are easily recognized, even if only the cephalis be developed. 



The primary arches between D, Lj. and Lj are well developed, 



and protrude on the inside like three archshaped ledges, running 

 upwards. By means of outwards and downwards bent byspines 

 from these primary arches, together with branches and arches from 

 the dorsal spine, A, and the lateral ones, the thorax is developed. 

 In the upper part of the thorax, there are, therefore, formed 

 three, more oi- less distinct swellings, a right one, beloAv the pri- 

 mary, right, lateral arch, a left one, below the left, lateral arch, 

 and a ventral one, below the primary, ventral arch. 



Here too, as in all the forms of Cyrtoidea occurring in my 

 material, there is an inner axial spine, pointing downwards verti- 

 cally from the ventral end of the central rod, thus having the same 

 starting point as the ventral, sagittal spine. 



L. setosa Juhg. 

 (PI. XVI, figs. 81—83; pi. XVIII, fig. 108). 



JøkctEnsen L. 91, p. 91. nou Botryopijle setosa Cl. L. 30, p. 

 27, pi. 1, f. 10. 



Compare above the description of the genus and of the structure 

 of the species in the introduction to the group Nassellaria. Cfr. 

 too Jørg. 1. c. where a detailed description will be found. 



Of byspines, there are usually too strongly developed one on 

 the right, lateral arch, protruding in the form of simple spikes in 

 the upper part of the thorax, one or two similar ones on the left, 

 lateral arch, and a couple on the cephalis. 



The spikes, which are seen in vai-ying numbers and differently 

 developed on the lower margin of the thorax are — at any rate 

 most often — only temporary formations. They disappear later on, 



