Mr. C. Mcrcschkow.sky on Scll.i;i1iora. 187 



Sellaphora piipula (Kiitz.), Mer. (PI. IV. figs. 1-5.) 



Navkuht pupnla, Kutzin<r, llacill. p. O-"', pi. xxx. fig. 40; Cicve, Syn. 

 Navic, Diat. imrt i. p. l.''*l. N. pupwa,\i\.t. geyiuina, ftrun. Aivt. 

 Diat. p. 4-'), pi. ii. fig. -"53 ; Van Ileurclf, Synops. p. 106, pi. xiii. 

 figs, lo, in. Sfd'inineis Witrockii, Lagovstadt, Spitsb. 1). p. .'iS, 

 pi. ii. fig. lo (1873) (according to Cleve perbaos Nnv. bacillifonnis). 

 StaiirnneiA tatrica, Gutwinsky, Mater, fi. rjalicyi, 1890, p. 24, pi. i. 

 fig. 20 (according to Cleve perbaps N. hacilliformis). Schizustauron 

 ? tatrica, De Toni, Xotarisia, 1890, p. 19G. 



The endochrome of this species is comjDosed of a sin^^le 

 plate resting with its median part on the surface of one valve, 

 ■which we may call the dorsal valve, the opposite one (the 

 ventral valve) being always without an endochrome. The 

 median or central part [m.) resting on the valve is narrow, 

 extending transversely from one side of the valve to the 

 other, and terminating in four lateral prolongations {pr.) which 

 rest on both connecting-zones. When seen from the valvular 

 aspect (figs. 1, 3, 4) the central part appears as a light yellow 

 transverse band with concave margins and the zonal parts as 

 two narrow dark lines along the sides of the frustule, reaching 

 its extremities. Tiie four prolongations are always of equal 

 length : sometimes their upper margins are partly turned on 

 the dorsal valve, where they appear as a light band (fig. 1, a) 

 gradually passing into the central part (fig. 1, rn.) ; such a 

 case is represented in fig. 1 ; but usually the prolongations do 

 not extend on to the surface of the valve. The zonal aspect 

 shows a short dark band [iv^. 2, m.) on one side of the frustule 

 in its middle part, which is nothing but the median 

 portion of the plate seen in projection : the connecting- zone is 

 occupied by a broad light plate {pr.), which corresponds to 

 the dark lines pr. of figs. 1, 3, 4; it never reaches tiie 

 margin of tlie frustule opposite that which contains the dark 

 band (?».). The endochrome is of a light yellow-brownish 

 colour. No pyrenoid is to be seen. 



A very peculiar feature of this species consists of the two 

 free ela^oplasts, or libroplasts as I propose to call them 

 (fig. 1, //;.). They are situated along the median line of the 

 valve, one in the upper, the other in tiie lower iialf of the 

 frustule, and, as can be seen from fig. 2, they byth rest on one 

 valve, which is always the ventral. These libroplasts are 

 absolutely coTistant ; I have found them in all the numerous 

 specimens which 1 have had the opportunity of observin-i- 

 and they are invariably two in number, always occupying- the 

 same position. It is as good and constant a characteristic of 

 this species as the disposition of stria3 or the form of the 

 terminal nodule. The shape of the libroplasts is rarely a 



