Navivnlarea.'] infusoutac antmalottt.ks. 475 



frushiles cohering by tlie angUs, lungitiidinally striatod. Differs fi'om 

 Aehnantkes, by its frustulos cohering at their angles, and having 

 longitudinal strios. It differs from Tessella only in the stipitate 

 filaments. 



" The two series of longitudinal stria) in Striatella exist also in 

 Tahellaria, Tessella, and Tetracyclus. The appearance of longitudinal 

 strise is in fact produced by siliceous plates, arising internally fi-oin 

 the margins of the jSlament, and extending towards, but not reaching 

 the centre. The interior is thus divided into chambers, opening into 

 a central space. Wlien viewed laterally, this central space has the 

 appearance of a canal, especially as the inner edge of each plate has 

 a concave outline." 



The genus Striatella of Kiitzing, does not correspond with that of 

 Ehrenberg ; it is represented but by one species, S. uniptmctata, 

 which = Tessella arcuata (Ehr.) The genus is thus defined : — 



" BaciUi tabulate (longitudinally vittate), vittoe pervious, numerous, 

 dense, band-like, stipes lateral." 



In the notes on S. unipunctata, Kiitzing says : " The tables (bacilli) 

 are mostly single, rarely conjoined ; large and small forms are often 

 collected together. The stipes is not always to be found, and may 

 be easily overlooked on account of its translucence. The chain-like 

 forms represented by Greville, I have not seen ; and they probably 

 rather belong to the genus Hi/alosira." Striatella gives name to the 

 family Striatellece, which includes also the genera Tessella, JTi/alosinr, 

 and RJiahdonenia. 



Steiatella Thienenumni = Tetracyclus lacustris (Kiitz.) — Testulos 

 elegant, closely resembling those of Striatella arcuata, but gibbous 

 laterally at the middle. Found by Ehrenberg in eaith, from Iceland ; 

 also living, in England and Wales. 



S. arcuata = RJuibdonema arciiatum (Kiitz.) — The curved striatella. 

 Tabiilar, nearly square, having from three to seven internal longitu- 

 dinal lines ti'ansvcrsely striated. The clusters of banners form 

 curved ribbons ; granules yellow at first, but become reddish or 

 violet. Fig. 203 represents two and-a-half tablets, with dispersed 

 granules ; and fig. 204, an old one with them united. Length of 

 single lorica l-570th to l-200th. On marine Algas. 



1 I 2 



