BY G. I. PLATFAIR. 323 



Genus Cosmarium Corda. 



Cos. HECTANGULARE Var. NODULATUM f. MINOR Playf. 



Long. 40, lat. 31, ap. 12, istli. 10 /z. Noduli apicales abfuerunt. 



Lismore (185). 



Cf. Polym. and Life-hist., p.476,Pl.iii.,f.5. The apical nodules 

 are sometimes wanting in these forms of Cos. rectanyulare. 

 (Pl.xli., Ill a). 



Cos. RECTANGULARE Var. BOLDTII f. MINOR, n.f. (PI. xli., f.ll6.) 



Forma minor, angulis basalibus magis rotundatis; lateribus e 

 basi levissime divergentibus. 



Long, semic. 12, lat. 22, ap. 10, isth. 10 /x. 



Lismore (185). 



Found only as companion-semicell to one of the previous form 

 (nodules present, however), Cos. recta7igulare iorma, Boldt, Desm. 

 Gron]., T. i., f.l8, to which I gave the name var. Boldtii in Some 

 Syd. Desm., p.613, measured 43-44 x 34-36 /x. This form, though 

 only about one-half the size, is almost exactly like Boldt's figure. 

 Cos. RECTANGULARE var. BiRETUM, n.var. (PL xli., f.l2.) 



Forma parva; semicellulse insequaliter hexagonse; e basi plana 

 lateribus levissime divergentibus (paullo magis quam in var. 

 Boldtii f. minore) ad apices rapide convergentibus ; apicibus 

 truncatis paullulo productis; angulis lateralibus latissime-rotund- 

 atis, basalibus obtusis; isthmo angusto. Membrana levis infra 

 apicibus papillis singulis interdum ornata. 



Long. 25, lat. 22, basis 19, ap. 8-9, isth. 6/x. 



Lismore (185). 



Forma rectilinearis, n.f. (PI. xli., f.l3). 



Forma lateribus rectis, apicibus non productis, angulis laterali- 

 bus obtusis nee rotundatis. 



Long. 27, lat. 22, basis 19, ap. 8, isth. 6 /x. 



Lismore (185). 



Forma angustior, n.f. (PI. xli., f.l4.) 



Forma angustior, parte superiore laterum retusa. 



Long. 26, lat. 20, basis 16, ap. 8, isth. 6 /x. 



Lismore (185). 



Something like Cos. {Eu.) leiodermum Gay, Conj., p. 58, PL i., 

 f.l6j which itself is a form of Cos. rectangulare Grun. Differs 



