MAKiT — DIATOMS OF THE ALBATROSS VOYAtiES. 289 



TRIGONIUM Cleve. 



Trigoniinn Clovo, Ofy. Kg]. V('t. Akad. 24: Clili. I8(J8; Bill. Sy, V^^t, Akad. Ilandl. 

 l^-': S. 1873. 



Triraratium Ehrenb. tn\ dct. Bail. Smithsoiu C\m(r. Knowk 2'*: 14./. 5.5-,5^. 1851. 



Ihiglit. Quart. Joiirn. Mi<T. Sci. 4: 275. pi. 77./ ;6\ 185G. 

 Biddidphia Gray, in part; Briglil. Quart. Joiirn. Micr. Sci. 7: 181. pi. 9.f. 15. 1859. 

 Z[i(jocerosYA\ximh. in pari; Baik Smithson. CVnitr. Kncnvk 7: 11. j>?. I.J, ^9. 18-54. 

 Amphitetras Ehronli. in part; l)v Tonl, Syll. Alg. 2: 900. 1894. 

 AmpMpnitas Ehronb. in part; Pe Toni, Syll. Ali,^ 2: 911. 1894, 

 Nofhoccmlium Do Tuni, Syll. Alg. 2: 014. 1891, in part. 

 Ci'slodlscus Grev, in part; Gruii. in Van Ileur. Syiiop. pi. 12G.f. 1-2, 1881. 

 r::^cudol nveralium Gnm. Drnksclir. Aka(L "W'icii 48-: 8:k 1884. 



The g(Mnis Triceratiuni as constituted Ijy Ehrenl>erg<^ included sim]>ly triangular 

 speeiniens of the genus Biddulphia Gray. The striking but inconstant characteristic 

 led him to select the very descriptive name and to word Ids diagnosis so as to convey 

 this one idea. His tyi)e species, T. faius, agriM's willi this. It is, therefore, leased 

 on a wliolly untenable eoTu-epticm and is a synonym of Biddulphia. Gradually, 

 how(^Yer, it underwent modilieation chiefly at the hands of Brightwell^ and Ilalfs^c 

 whereby it came to incbule forms with men* than thr(H' horns, together with a host of 

 forms where the liorns at the angles are obscure or wantijig, in fact, almost anything 

 of a polygonal character, wlu^n seen from the vulval side. It thus came about that 

 the genus grew to be a mixture of many genera, whose sole bond of union was the 

 worthless accident of a more or less angular valve ouiline. Thus polygonal specimens 

 of Stictodiscus Grev., of Ditylum Bail., of the triangular forms of H<*mianlus Elmnib.j 

 wdiich make up Heiberg's invalid genus Trinacria, of the triangular fcirms of Terpsi- 

 noe Elir(^nb., w^hich Wallicli (^alls Ilydrosera, and others found a resting }>lace in 

 this unsci(mtific medley. De Ton L^^ performs the useless task of restoring it to its 

 original boundaries^ except that he excludes those triangular forms represented by 

 Grt^ville's newer genus Entogonia. It is evident that Triceratiuni Ehrenb, represents 

 nothing but a peculiar configuration of Biddulpliia; nor have th(^ attempts to recon- 

 struct it resulted in anything but confusion. It must, therefore, be abandoned, a 

 course adopted by Van Ilourckj Boyer, and tuht^rs. But in doing this some diatoms 

 now bearing the name Trieeratium remain which can not l)c referred to any of the 

 before-mentioned genera. * This has led to th(* necessity of a genus for these forms; 

 and I liav<i placed them in the genus created ]>y Cleve for this purj)ose. Ib^ delines 

 it as follows: "Hufvudytan triangular, sidoytan rcktangdforinig utan framspringand(^ 

 utskott (41er horn.'' It is true that this is too inch'fi]ut<% as it would inchuU^ such Iri- 

 angtilar and quadrangular forms as we ukh^ with in. Stictodiscus^ as well as the mem- 

 bers of the genus Entogonia, a genus that (deve recognizes as distinct; and further 

 would exclude the occasional biangular or fusif(jrm specimens of some species nor- 

 mally triangular. But that the latter are not int(^nded to be excluded by Cleve is 

 shown by the fact that in disctissing Trigonium atrticum (Bright.) Cleve ^lu; spi'aks 

 of the l)iaiigular variety known as Zy(jocero.s halaena Ehrenb. B(tyer/ refers the 

 mend)ers of Triceratiuni (i'xclusive of those n^ferred to other established genera, as 

 Stictodiscus and Ilemiatdiis) to Biddulphia, wdiether the angles are surmounted by 

 horn-lik(^ processes or not^ and to a great extent Van Ileurck does th<^ sam(\ This 

 takes from Biddulphia its most salient charac1eristi<' and places in the giMuis such 



^ Phys. Abh. Akad. Wiss. Berk 1839: 129, 159. 18-11. 



tQuart. Juurn.Micr, Sci. 1: 215. 185:5. 



c Britch. Hist, Inf us. ed. 4. 853. 18G1. 



c^De Toni, NotarisiaS: 912. 1890; Syll. Alg. 2: 917. 1894 



cBih. Sv. Vet. Akad. Handl. 1'^: 8. 1873. 



/Proc. Acad. Phila. 1900: 190E 



