290 CONTRTBTTTTONS FKOM THE KATTONAl. HKTiBARTUM. 



dialoms a? tlinpo in iIk* following '^pooios whirh are in striking ronlrast to tlio T^itkhil- 

 pliia idea. I tlKTcfore make use of Heve's gt^nus, excluding iho-^o triangular forms 

 that have definite C(^ntrul ureas distinctly differeni in ticulpture from the rest of the 

 valve, represented by the genus Entogonia, and in(duding forms having four or more 

 angles. Nothoeeratium De Toni agrees in part with this, except for the limitation 

 of the species to those of six or more angh^s, an utterly im])ractical)le ]U'ovision, 

 leading to the absiu'd distinct i(m between llu^ four-sided and the six-sided sp(^ci- 

 nnms of Triceratium paralUiiuti (Irev.," the former of which he i)laces in the genus 

 Amphitetras and the latter in Nothoeeratium, 



Trigonium alternans (Tjail.) Mann. 



Tjiceratium alternans lUiil. Smilhson. C<mtr. KtiowI. 2^: 14. -pi. l.f, 55-56. 185]; 



2«: 40. 1851. Briglil. Quart. J<mrn. Micr. Sci. 1: 251. pi 4 J. 19a-h. 1853. Jan. 



Aldi.Schles. Ges.Vaterh(Hilt. 1862-: \b, pL 1 A. f, 16.mV2. \V. Smith, Synop. 



Brit. Diat. 1: 2fi, pi. 5.f. 45, pi. 30. f. 45, 185:^. Schmidt, Atlas pi. 78. J. 9-18 



(not/. 19-20, = T. campccJdanmn Gnin.). 1882. O'Meara, Proc. Roy. Irish. Acad, 



IL 2: 278. pi 27. f. 11. 1875. Van Heur. Synop. pi 113, f. 4-5, 1881. Pritch. 



Ilist. Infus. ed, 4. 854. pi 6. f. 21, 18G1. Moub, Diat -taf . pi l.f. Wa-h, 1890. 



"Wolle, Diat. N. A. pi 100. f. IC, IS (not pi 100. f. 2), 1890. De Toni, Syll. Alg. 2: 



941. 1894. 

 Biddidphia alternans Van Heur. Synop. 208, 1881, Boyer, Proc, Acad, Phila. 



1900: 719. 1901. 

 Triceratium ranabile Hright. Quart. Journ. Micr. Sci. 4: 275. pi. 17. f. 19a-c. 185G* 



Moeb. Diat.-taf. pi D.f. 19a-c. 1890. AVest, Trams. :Micr. Soc. Lond. n. s. 8: 149. 



pi l.f, 7. ISGO. Pritch. Hist. Infus. ed. 4. 854. ISGl. Lend. Fort. -Mem. Soc. 



Emul. St. Brieuc GO. 1879. 



There is a spt;cious resemblance here to the Biddul]>liia type in the slight elevation 

 of the angles and this is intensified by their being apparently cut off from tlu; rest of 

 the valve by deihiite internal septa. This is especially so if sevc^ral of the figures above 

 cited are relied on instead of the diatoms tli(;mselvt*s. That there are no processes at 

 the angles can be seen by a < an^ful examination of more than one specimen of this 

 species. Somt^times th<^ extremities of th<^ angl(\s are not raised at all above the rest 

 of the valve and in some cases they are slightly lower. The lines usually (not always) 

 marking off the <^xtremiti(\s and making them resemble Bid<lulphia processes have 

 no significance; for in the forms classed by Brightwell. as T. rariahile^ the valves 

 are penetrated by numerous false septa extc^nding inward from the margin. The 

 angles are often beaded exactly like the rest of the valve. Altogether these angular 

 portions are very dilTerent from the true processes of Biddulphia. It may be men- 

 tioned in this coiuiectiun thuL the frustules are lujt joined by alternate angles into a 

 zig/ag chain, as is common in Biddulphia, but wln^n united, which is rare, it is face to 

 face; but it should also be said that too mudi significance should not be placed on this 

 fact, either her<^ or idscnvluTe. Scdimidt, De Toni, and otluTs do not admit this species 

 into Biddulphia, but retain il in Triceratiiun. 



Found at station 3696, off Honshu Island, Japan. 



Trigonium articum (Ih-ight,) Cleve, Ofv. Kgl. Vet. Akad. 24: GG3. 1868; Sv. Vet. 

 Akad. HandL 1'=^: 8. 1873. 

 TricerathiTR arcticum Bright. Quart. Journ* Mier. Sci. 1: 250. pi. 4- /< 11- 1853 

 Mo(^b. Diat.-taf. pi l.f, 11. 1890. Grun. in Fenzl, Reise NovaraBot. 1: 24. 1870. 

 De Toni, SylL Alg. 2: 920. 1894. Pritch. Hist. Infus. ed. 4. 85G. 1861. Cleve & 

 Grun. Sv. V(^t. Akad- HandL 17-: 15, 111. bSSO. Schmidt, Atlas pi 7(1 f. 29, 

 pi 79. f. 5-6, S, 10 /;?.1882; plSl.f. 4-^^^^- IL L. Smith, Sp. Diat. Typ. no. 596. 

 1874. Van TTcnir. Synop. pi 112. f. 7. 1881. 

 Biddulphia arctica Doy<^r, Vvoc. Acad. Pliila. 1900: 714. 1901. 



a Trans. Micr. Soc. Loud. n. s. 13: 104. pi O.f, 22-23, 1865. 



