BY G. I. PLAYFAIR. 617 



difference is in the end-view, and the two conspicuous granules 

 above the isthmus are replaced by three low papillae above the 

 middle of the semicell, which show in the end-view as a very low 

 flat elevation. The produced apex is caused by ten granules 

 which appear in end-view as an oblong, four in front, four 

 behind, and an intermediate one on each side to complete the 

 rectangle. 



Var. imperfectum, n.var. 



Forma paullo longior quam forma typica, angulis basalibus 

 fere rectis, lateribus magis convexis, infra apicem granulis 

 obscuris 4, infra margines laterales serie una tantum granulorum, 

 supra isthmum granulis nullis. A vertice semicellulae ellipticse 

 utrinque medio scrobiculatione, apicibus rotundatis leviter angu- 

 latis, granulis in seriebus transversalibus. 



Long. 32; lat. 27; crass 16^ 



Guildford (23). 



This probably develops into var trifoliatum, the scrobiculation 

 at each side in end-view being an indication of the papillae about 

 to be formed. With the above compare Cos. Boeckii Wille, 

 Norges Fersk. T.l, f. 10; Cos. didymochondrum Nord. & Wittr., 

 Desm. Ital. T.12, f.ll; and Cos. aphanichondrum Nord & Wittr., 

 I.e. T.12, f. 12, which belong to the same group of desmids. In 

 Cos.jluvialile Playf., the sides are not crenate, and the papilla? 

 are conspicuous (cf. subsp. bipapillatum West, Frw. Alg. W. Irel. 

 p. 157) whereas in Cos. Boeckii they are very low and obscure, 

 and hardly noticeable in end-view. 



Cos. uliginosum, n.sp. (Plate xiii., fig.6). 



Cos. mediocre, oblongum, dimidio diametro longius, medio sinu 

 brevi acuto constrictum. Semicellulae subcirculares, angulis 

 basalibus fere rectis, crenis marginalibus circ. 15, granulis magnis 

 irregulariter (vel plus minus in quincuncem) dispositis, ornatse, 

 inter granulos binos punctis singulis. A vertice ellipticae. 

 Nuclei amylacei bini. 



Long. 51-56; lat. 36-39/x. 



Coogee. 

 47 



