.MANN DIATOMS OF THE ALBATROSS VOYAGES. 369 



Mastogloia, bul wv can nol for thai reason divide N. cuspidata into two genera, [n fad 

 in Borne Bpeciea of Mastogloia we find a close approximation to the craticular plate by 

 the extension of the marginal plate- toward or to the center of the valve, as in M. 

 fmifAuThwaites, a a form called for thai reason Navicula biscalaris bj Brebisson.6 



'I here is, however, some reason, despite th< ections, for admitting the 



genus, namely, thai true examples of Mastogloia always have, bo far as I know, these 

 marginal internal loculi and are thereby rendered widely distincl in appearance from 

 any Navicula. As for their mode of growth, i. e., the individuals being embedded in 

 gelatinous masses, this can qoI be taken into accounl here for the reasons mentioned 

 under Cocconema. Besides, as < rrunow points out, c living specimens of Mastogloia are 

 often found withoul this gelatinous matrix, [t seems best, on the whole, to recognize 

 the genus subjecl to the foregoing remarks. 



The admission of Ehrenberg's genus Pleurosiphonia as a Bynonym is also open to 

 question. Mosl authors overlook it entirely. Thus 1 can find do reference to it in 

 Cleve's extensive work on the naviculoid diatoms, d I >e Toni< recognizes it as a distinct 

 genus unli Beven Bpecies. Ralfs, /though giving it a place in his classification, 

 "The characters of this genus are unknown to us they were nol given by Ehrenberg till 

 ten year- later 1^7<i : bul from Ehrenberg's figureof /'. affinis we think it isprobably 

 identical with Mastogloia." Even the diagnosis does not quite Bettle tin- doubt. 

 There is no exact mention of marginal loculi, bul of "siphons" whence the nan • 

 either side as lateral lines. These, which Ehrenberg Btates are "saepeaere repleto," 

 are bo figured in all the above citations, and in every case they are drawn as within the 

 marginal Bpace occupied by the loculi of Mastogloia; that i-. nearei the center of the 

 val\ e; and invariably as unbroken tubes, qo1 as rows of chambered loculi. a fact empha- 

 sized in the diagnosis by the word "simplice." Bui no Buch diatoms have ever been 

 met with. Thenearesl thing known is Mastogloia, and it is reasonable to suppose with 

 Half- that Ehrenbem was dealing with specimens of Mastogloia. Pleurosiphonia ap- 

 pears in literal ure three year- prioi to the making of Mastogloia ; thai . is in 1853. But 

 this is without figure or description, a nomen nudum. Ehrenberg's Iiu r ure precedes 

 Thwaites's publication by two years, bul the diagnosis does not occur till l s 7n. 

 the title •" Nova < Jenera. " > See citation above. ) The generally recognized ruleof bot- 

 anists that the date of a name shall resl on its diagnosis rather than on an undescribed 

 figure should not be used too strictly with the Diatomaceae; for, as a rule, figun 

 worth much more than any diagnosis, as the intricate sculpture of the diatoms, on which 

 their L r enus and species depend. i< possible to figure but well-nigh impossible to 

 describe. Besides, the reason for this rule in higher plants, -cod catalogues, and 

 similar non-scientific publications, plays no part with the diatom-. I would not. 

 therefore, as a rule, make the diagnosis the chief factor in fixing the date of a genus or 

 species in the Diatomaceae. Bu1 in this case, where the figures are al besl indefinite 

 and the diagnosis does nol appear till four years laterthan Thwaites's accurate liL:un-< 

 and description, 1 give preference to the latter. 



Mastogloia lemnisca Leud.-Fort. Mem. Soc. Emul. St. Brieuc :'.">. pi. S. f. ■>. L879. 

 Schmidt, Atlas pi 186. f. /, 15. L893. De Toni, Syll. Alg. 2: 324. L891. I 

 Sv. Yet. Akad. Ilamll. 27 : L59. pi :. /'. '.. L8 



My Bpecimen exhibits the markings of the variety represented by Schmidt '- figure 1 1 

 above. 



Found at station 3013H, Hawaiian Islands. 



"\V. Smith. Synop. Brit. Diat. 2: pi 

 Mn lit. January, I - 



<\'erh. Zool. Bot. Ges. Wien 10: 575. L860. 

 *Sv. Vet. Akad. Bandl. 26-: 1894; 27 : , 

 ' De Toni. Syll. A.lg. 2: 326. 1891. 

 /Pritch. Him. [nfus. ed. i. 915. L861. 



