BY G. I. PLAYFAIR. 611 



of crux australis. In size they tally fairly well also, and the 

 agreement of West & West's figures with those given by Raci- 

 borski is marked: Turner — long. 120-135; lat. 80-97; crass. 44-50; 

 lat. apic. 50-56. Raciborski— long. 120-130; lat. 105-125; crass. 

 55-65; lat. apic. 57-77. West & West— long. 135; lat. 102; crass. 

 57; lat. apic. 76. 



I cannot see any particular reason for placing Mobius' plant or 

 any of these forms under Micrasterias. Generally speaking, the 

 membrane in that genus is delicate, and at most puncto-granulate 

 or slightly scrobiculate. It is in Euastrum and Cosmarlum that 

 we meet with the strongly verrucose or scrobiculate membranes 

 and tumours. The rugged character of the membrane, and the 

 scrobiculate or verrucose tumour in these desmids should, I 

 think, create a presupposition in favour of their being Euastra. 

 Other points are the great thickness of the cell in end-view, and 

 the disposal of the endochrome in four parietal plates, which link 

 them to such forms as Cos. amplum, Cos. rnagriificum, Cos. 

 tholi/orme, etc. 



Var. Auburnense, n.var. (Plate xii., fig.2). 



Forma paullo major, sinu apertiore, lobo polari truncato, angulis 

 granulatis, sinu inter lobos apertiore acutangulato, supra isthmum 

 tumore magno scrobiculato, scrobiculis plus minus in quincuncem 

 dispositis ornato. Lobi laterales angustiores extrorsum attenuati, 

 apicibus bifidis sed minime incisis, margine.s versus granulati, 

 tumoribus minimis geminatis binis (et tumore unico introrsum) 

 instructis. A vertice semicelluke ellipticse in medio latse, utrinque 

 tumore scrobiculato instructs, polos versus acuminata?, apicibus 

 obtusis, prope apices tumoribus minimis binis utrinque proji- 

 cientibus. Lobus polaris angustissimus, apicibus non bifidis. A 

 latere semicellulse pyriformes, a tumoribus ad apices rapide 

 attenuatse, apicibus obtusis. 



Long. 132-168; lat. 1 16-144; lat. lob. pol.96-108; lat. coll. 70-84; 

 lat. isth. 40-48; crass. 72-76/x. 



Auburn (47). 



This form has the polar lobe undeveloped, compared with the 

 rest of the cell. I consider it an occasional variation, inter- 



