221 



duration aiul tliat thus fossil valves Avill ciilarLrf the apjiai-cut area 

 of distribution of the still livin;^' species. 



Most of the species of this i.-'rouj) 111 aic jnoliahly recent 

 OIK'S, a y^reat number of them beiny olisrrvcd alive on the west 

 coast near Heriren. 



Next to srroup 111 it is i;iou|i \'. which contains the greatest 

 number of species. Many of tlieni have a pi'edominating- southern 

 distribution, but occur, uune or less freriueiitly. as far north as the 

 coasts of the North Nea. To this group belong tlie following (a few 

 of wliich might perhaps rightly be reckoned to anotiier group): 



Vv.-citiudi^ciis Botliii. 



Biddulphiu pHlchella (a broken 

 valve, Tromso, Cl.i. 



B. regina (only exceptionally found 

 as far north as Scotland I. 



B. faviis (once found in Spits- 

 bergen). 



J5. alter Hci) IS. 



B. punctata. 

 Syneåra undulata. 

 S. Hennedyana. 

 Raphoneis nitida. 

 Dimeregramma minub-. 

 £>. fulvitm. 

 Gbjidiodcsm is distans. 

 Grammatophora serpentin<(. 

 Nitzschia punctata. 



N. acuminata. 

 N. hilohata. 

 2s. lancflolata (a). 

 Canqiylodiscus eximius. 

 Surirella fastuosa. 

 Achnanthes longipes. 

 Phuroneis distans. 

 P. hritannica. 

 DonVmia recta. 

 Pleurosigma rig id urn . 

 P. formosum. 

 P. speciosum. 

 P. halticum. 

 Scoliotropis latastriata. 

 Caloneis consimilis. 



C. Uanda. 

 C. iiiusca. 



Ibtauroncis .•adiiin. 



Navicula moniliformis. 



N. latissima. 



K. compressicauda. 



N. superimposita. 



K. palpchralis a, var. Barclayana, 



var. (iiigulosa. 

 iV. pnetrxfii. 

 N. clanita. 

 y. forcijxitd rar. 

 Fiinidhirid cluriculus. 

 P. Tn-rrlipiua. 

 Diploneis coff'eiform is. 

 D. lineata. 



D. (contiguii var.) eudoxia. 

 J). notidiUts (var. explrta). 

 D. fusen var. (jregorii. 

 D. nidjar. 

 D. nitvsrrvs. 

 1). sejddrld. 



D. didiidid. 



D. cher.iunt'Hsis. 



D. crcdiro et var. paiidura. 



Mastogloia apiculatu. 



Ampliora protcds var. eontigua. 



A. macilenta. 



A. costafa. 



A. hinodis. 



A. sule.dtd. 



A. dldfd. 



A. ohtu.^-d. 



A. spectabilis. 



A. ocellata. 



Epifhemia mdsculus. 



Many of these species were for the first time described and 

 illustrated in the work by Gregory above mentioned. 



All these species have not previously been mentioned from 

 the arctic zone. To this group should properly also most of those 

 be i-eckoned which are previously known from the arctic zone, but 

 only from the coast of Nordland („ Finmarken"). 



Less numerous are the species of a mere western European 

 distribution, group IV. Such species are, however, on the whole 

 not numerous. Here belong the following species: 

 Coscinodiscus diwUinis var. (west C. Nonmmni. C. fuscieulatus A. 

 coast of Norwav). Sch.ai. 



Actinoeyclus crassus. 

 Aetinoptychus s})lendens. 

 Bidduljili ia turgidd. 

 Synedra ktculds. 

 A'itzscliiu litorea. 

 N. naricularis (Spitsbergen?). 

 Campylodiscus par rains. 

 Coeconeis lyra (west coast of 

 Norway). 



These species, the first and the last ones only excepted, are 

 common to Great Britain and Norway. 



A closely related group is g'roup II, including species with a 

 predominating western area, though also occui'ring right up to the 

 arctic zone. These are the following: 

 Coscinodisc us Kiitzingii. 



Flcurosigma attcnuatum (^). 

 Caloneis liber. 

 Schizonema crucigcrum (Y). 

 Naricula northumbrica. 

 N. peregrina var. hfwingensis, 

 N. prasccta (west coast of Norway). 

 Diploneis hyperborea vai". excisa 

 (west coast of Norwav). 



Hyalodiscus .scotieus. 

 Biddulphia rhombus. 

 B. Smithii. 

 Nitzschia apiculata. 

 Campylodiscus angularis. 

 Ehoicosigma arcticum. 

 Caloneis brevis. 



Narieula dirrcta et var. subtilis. 



N. fortis. 



N. distans. 



N. palpehralis var. semijdena. 



A", pygnuea. 



Diploneis hyalina. 



Amphora lævis. 



The genuine arctic species, belonging to gToup 1, are few 



Nitzschia Mitchelliana. 

 Gomphonema Icam isehatieum. 

 Amphora groenlandica. 

 Diploneis entomon Cl. p. p. (^ 

 D. sdheinetd var. niedid). 



Coscinodiscus borecdis. 

 Aeiinoeyclus cdienus'Y 

 Bidddlphid drcticd. 

 Syncdrd kam tscha ticum. 

 S. rostellata. 

 Grammatophora arctica. 



All these species, except the last one, are besides very rai-e. 



At last we have the remarkable group VI of only southern 

 forms, partly only known from regions situated far to the south or 

 even only from the tropical zone. Their distribution (as earlier 

 known) extends northwards only as far as to the Mediterranean. 

 To this group belong: 



Nitzschia (insignis var.) t^jiafhu- 



lifei-a 

 N. coarctata. 



N. (Smithii var.) notabili.-<. 

 Amphora Grwffii. 



(Coscinodiscus leptopus i-erxis 

 C. nodulifer. 

 Aulacodiscus Kittoni. 



A. ■Johnsonianus. 

 Bidddlphid regina var. 



B. Idtd. 



There may, however, be some doubt as to whether the ibrms 

 observed of Biddidphia lata and Amphora Græffii ai'e identical with 

 those, which usually occur in southern regions. Moreover, Coscino- 

 discus leptopus, Nitzschia spathulifera, N. coarctata, N. notahilis and 

 Biddulphia regina var. are all veiy rare and scai'ce. There remain, 

 however, Coscinodiscus nodtdifer and the two species of Aidacodiscus, 

 all of ^\-hich occur in compai-atively large numbers, and in several 

 samples. These species are easily recognizable, and have a pro- 

 nounced tropical area of distribution. 



Probably these species are all fossil, but T cannot at present with 

 certainty decide this. Coscinodiscus nodulifer has most prol)ably 

 occurred as a plankton species. 



All the species of groups IV. V and W, a considerable number 

 of species in all, have not before been known fiom the arctic zone. 



