26S ('ONTRIBUTIOXS FROM THE NATIOXAL IIKUBAHTUM 



The matter uf this conlusitJii has been m extensively Irealeil l>y Castracane'^ that no 

 attoni[)t ti) add to what is there said is necessary lu^re. Tlif snhjec t will )k^ n*f(Tred 

 to in this report under the <j;enns Trigonimn. The 2>resent ^enus is in some instancies 

 so close to Ilemiptychns I^]hnMih. that good deiinitions [\rv hurd to fonnnlate.^ 

 Nevertheless the utility of the two u:cncra is c<jnsiderable, and their approach is not 

 cluse enough to merjje this ^enus into that of l'"!hrenl)eri];. 



Stictodiscus buryanus Grev. Trans, ^licr, Hoe* Lund. n. s. 9: 40. pi. 4-/- i-2. ISGL 

 Moeb. Diat.-taf. pi. Sl.f. 1-2. 1890. S<-hnudt, Atlas pi. ISl.f. S. 1888. Trnan 

 &. Witt, Diat. Ilayti ID. pi. 5.f. 1-3,5-6, 1'k 1888. Do Toni, Syll. AI-. 2: 13l:h 

 1891. 

 Siictf>(}i,'<cuii JtrdlUmferianiis Truaii & Wilt, Diat. Hayti 19. /)/. '). f. 11. 18S8. 



It is a question whetlu^r or not S. johii^onknwis Crov. should be placed here as a 

 synonym. The chief distinction is the sin^^le lint^s of radiutin^i; beads iu S. johnson- 

 ianiis and the multiple lines of beading, especially near the l)t)rder, in S. hunj- 

 anus. This <lifference, as seen in Greville's original figures and in ])late 5 of Lnard 

 and A\'ilt is hardly ade([uate to keejt these apart. There is even less excuse fur mak- 

 ing a new species of JS. hnlllimjrrianus on llu^ trivial ground that the shadow Viuv^ at 

 the center of the valve do nr>t anastomose. 



Fonml nt stations 2807, ;?7S4, Galapagos Islands^ and north of AhMitian Islands. 



Stictodiscus gelidus Mann, sp. iiov. Plate L, ficiiik 5. 



"\'alves circular^ almost flat; inarhcd with very large Hat disks, whicli, like the 

 interspaces, are smootli and shining; the largest, four to five in number^ arrang^nl 

 about the center of the valve in a ring, ea^h disk being one-eighth the diameter of 

 the valve in width or fully 0.01 mm. wide, lhen( e deiTeasing in size to the border of 



■ 



the valve, wdiere they are one-third as large; 12 to 18 r;i<liating but irregular liiu^s 

 prtH/eeding from the border toward the center, but not reaching it, as is common in 

 this genus; at the center one smaller disk invariably perforated l)y a vermiform central 



pore, larger above an<l narroAving inward lo a tine point; rim narrow and hyaline. 

 Diameter of valve. 0.058 to 0. 105 mm. 



Typo in the V. S. National Museum, No. 500124, from station -102DII, Bering Sea, 

 June 27, 1900; 913 fathoms, bollom uf gray sand and clay. 



Stictodiscus johnsonianus (irev. Trans. Micr, Soc. Lond. n. s. 9: A^. pL 4.f. S. 



18G1. De Toni, Syll. Alg, 2: 1314. bS91. Truan & AVitt, Diat. Hayti 20. pL 8. 



/. 4. .9, pi. 6./. 16. 1888, Moeb, Diat.-taf. pi 37. f. 3. 1S90. 



Sticlodiscus jeremiantts Castr. Rep. A'oy. Chall. Hot. 2; llfi. IHSti. Truan it Witt, 



Diat. Ilayti 20. pi 5. f. 10^ pi. 6.f.£. 1888. Schnudt, Atlar. j^llSl.J. 1. 1888. 



DeToni, Syll. Alg. 2: 1320. 1884. 



Triarnfiitni jrrrmiamtm Schmidt, Atlas pi. 75./. 2-2a. 1882. 



Stictodiscus truant Wilt, in Truan & Witt, Diat. Ilayti 19. pi. 4. f. 2S-24. 1888. 



Schmidt. Atlas p?. 731./. 2. 1888. Do Toni, Syll. Alg. 2: 1317. 1894. 

 Stictodiscus ramihicus Truan &, Witt, Diat. Hayti 20. pi 5./ 14. 1888. De Toni, 



Syll. Alg. 2: 1319. 1S9I. 



Stictodiscus radiatus Castr. Rep. Voy. Cludb Jiot. 2: 117. pi 1, / /. ISSG. De Toni, 

 Syll. Alg. 2: 131G. 1894. 



In admitting a specific difference between this diatom and S. htnijanus, diiefly on 

 the basis of the multiple character of the radial rows of l)eading in ihe latter and 



«rastr. Rep. Voy. Chalh Hot. 2: 112-110. TSSO. 



&Cf. Arachnoidiscus harbadcnsis Hchnndt, Atlas /)/. (iS./. IL \vh\i Stictodisru.s hard- 



manidfius Grev. pi 74-/^ S. and these tw<^ with Sliclodiscus grovei Schmidt, pi 147. 

 /. 5-7. 



