278 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Bail. J and T. {Av.lacodiscus) thumii Schmidt, a somewhat a1)crrant }>haso of the genus, 



for niotit nienil)ers uf Llie genus have sinipki beading for markings, radially arranged, 

 with a more or lesri pronounced hyaline central area Iioiu wliich hyaline lines run 

 to the bases of the interuiarginal procesises. Indeed, Eupodiscus of I'^hrt'ub. (not of 

 Ratt.) came to represent just the aberrant }>hase of T. cmjus. But the differences are 

 neith(T constant nor striking enough to warrant a separate g(nuis, and Tlatlray, Schmidt, 

 and others, have done rightly in uniting these with Ihose g'/m^rally called Auhicod iscus. 

 Battray has unwisely r(.^tained the name Eupodiscus lor a group of diatoms having 

 none of tlxe characteristics of Ehrenlicrg's forms, nor containing a singh' species so 

 named by him, namely, species with horn one to four processes that are not protuberant 

 horns, but more of the nature of the "ocelli'' in the gcinis Auliscus or of tlie pseudo- 

 nodide in Actinocyclus. TIu^ genus so franu^d is of doubtful value, and if it l)e needed, 

 those <jf its members which can not be refc^rred to Aulistajs (where most of them belong) 

 would be better place<l under an entirely new generic title, rather than under the mis- 

 leading name Eupodiscus, Eupodiscus Ratt. (not Ehrenb.) is therefore left ovit of 

 the above synonymy. ti 



Tripodiscus affinis (Grun.) Mann. 



Aulacodiscas ajjinis Gnxn.; Schmidt, At]^spLl,34'f- 0-10. 187(5. Ratt. Journ. Roy. 



Micr. Soc. 8^: 359. De Toni, Syll. Alg. 2: 1110. 1894. 

 Atdacodiscus chasvi Pant. Beilr. Racill. Ung. 1: 57. pi 29, f. 294. 18SG. 



Aulacodisciis oregonus sparsias-piindala(j)^\ii\,\ Schmidt, Atlas />?* 107. J. 6', 7 (figure 

 unnamed), 188G. 



Rattray includes in this species tlie unnamed figure of Schmidt's noted in the last 

 synonym as well as Grunow^'s subspecies of .1. orcgomis IJail. I think this union is 

 justified. But there seems to me more uncertainty about placing here the type and 

 varieties of .1. lunyacsctU Vwui,^ However, there is a similarity between these and 

 the above, and indeed between ail these and ^1. oregonus Baih 



Fomid at Station 300111, off British Colundna. 



Tripodiscus beringensis Mann. Plate L, figure 6. 



Valve circular, strongly marked with coarse beads, l>eco]ning smaller only near the 

 margin; processes nine, submarginal; from the base of each a hyaline rectangular 

 space, two roAvs of beads wide, extending radially inward for about one-fifth the 

 radius, from this point a single row of l>eads running to tlie small circular central area, 



this inclosed by a ring formed of the nine ternunal beads of these rows; the segments 



subtended by these nine radial rows si^t with beads of e(pial size in paralh'l lines, only 

 the central one in each segment being, therefore, radial. 



Diameter of valve 0,OG3 mm.; beads Gl in O.i mm. 



Type in the U. S. National Museum, No. 590130, from Station 402911, P.ering Sea, 

 Jiuie 27, 1900; 913 fathoms, bottom of gray sand and clay. 



Tripodiscus concentricus Ahmn, sp. nov. Plate LIV, figukes 1, 2. 



Valve circular, nearly flat for onedialf the radius, thence moderately and evenly 

 convex to the margin; marking of larg(^ l)eadSj of uniform size until williin one-fifth a 

 radius lengthof the margin, then of smaller beading, soplacc^d as to form a single spiral 

 about the minute hyaline center, thence passing into a series of strictly concentric 

 circles an<! the component beads of each circle so arranged as to form wilh those in the 

 other cin les pf i jctly radial rows, llie beads set slightly closer in the conceii! ric circles 

 than in tii(: rr _iiating rows; at the distance of one-half a radius from the center, where 

 the vah/9 "^ ^:*comes convex to the mari^fin. the two concentric circles of beads a trifle 



'^Cf. Jouin. Roy. Micr. Soc. 8-; 900. 1888. 



^Pant. Beitr lUcill. Tng. 1: &9. pi l.f- 2, pi 2,f, 9-10, pi 25. f. 225-229. 188G. 



