348 - FRESHWATER AL^ 01^ LISMOEE DISTRICT 



inferior linea centrali et fascia transversali instructa. Valva 

 superior striata taiitum, linea centrali nulla nee fascia. 



Long. 84, lat. valv. 18, frust. crass. 24 //. Striae 8 in 10 /x. 



Woodlawn (225). 



I can find no description answering to this form, in Cleve's 

 Synopsis. The stauros is 3 /x broad. 



AcHNANTHES EXIGUA Grun. (PI. xlv., f.25, 26.) 



Long. 13-16, lat. 6-7, ap. 3; frust. crass. 4 /x. 



Lismore(l76, 178, 190). 



Cf Schumann, Preuss. Diat., Nachtrag ii , PI. ii., f.59. This 

 species was found, in some quantity, along with Nav. 7ni7ihna 

 and its three companions (supra), and there was reason to believe 

 that its frustules had been originally, like the others, in long 

 filaments. Cleve, Syn., ii , p. 190, gives dimensions, long. 13-17, 

 lat. 6-6 /x. He places the species in a class of Achnanthes which, 

 he says, has affinities with the groups of Navictila, including the 

 four mentioned above. The chromatophores of all are of the 

 same shape, so that it is highly probable that this form is really 

 a Navicula, and that the AchiiantlLes-iQSitxxYe^ are merely tem- 

 porary. I could see no genuflexion in the sideview of the 

 frustules. 



Achnanthes linearis W. Sm. 



Long. 13-16, lat. 4; crass, frust circ. 3 /x. 



Lismore(178). 



Found in company with JcA. exigua, above, and the four small 

 Diadesmis-iovms, of Navicula. I had a suspicion that the latter 

 w^ere occasionally to be found curved in girdle-view. 



Genus S t e n o p t e r o b i a Breb. 

 Sten. anceps var. Heribaudii Playf. 

 Long. 105, lat. 6 /x. 

 Lismore (240). 



These Proceedings, 1913, p. 535, PI. 56, f.21. Syn., Steu. miceps 

 Her i baud (not Lewis), Diat. Auvergne, PI. v., f.4. Forms of 

 >S7e?A. auceps Lewis, { — Nitz. franconica Rein.) are widespread in 

 this country. 



