BY G. I. PLAYFAIR. 481 



which it leans to var. sulcatum, and is indeed the transition-form 

 between the latter and var. australe. 



Forma. (Pl.xiii., f.l4). 



Forma apicibus plus minusve acuminatis, ceteris ut supra. 

 Long.42; lat.38; crass. 24^. 



Guildford (6 9). Cum priori. 



This form shows the beginning of growth towards a truncate 

 apex and subhexagonal outline. 



Var. OCELLATUM, u.var. (Pl.xiii., f.l6). 



Forma incrassatione ad angulos laterales instructa. Pyren- 

 oidibus singulis magnis. Long. 40-42; lat. 34-35; crass. 20; isth.6/ii. 

 Guildford(89). 



The peculiar appearance across the lateral angles is not a true 

 ocellus, but apparently an incrassation. It seems to be one of 

 the ways by which the angle is obliterated. 



Yar. PATEREFORME, H.var, (Pl.xiii., £.18). 



Forma semicellulis subreniformibus; basi plana; angulis later- 

 alibus late rotundatis; lateribus levissime arcuatis ad apices con- 

 vergentibus; apicibus truncatis; angulis superioribus peene levi- 

 gatis. Long. 40-42; lat.3o-37; ap.l2; isth.8/i. 



Guildford(89), Canley Vale(llO). 

 Forma. (Pl.xiii., f.l9). 



Forma angulis lateralibus macula incrassata ornatis; ceteris ub 

 supra. Long.40-44; lat.35-38; basis 30-32; ap.l4; isth.8-10/[x. 



Canley Vale(llO), Guildford(I14). 



Yar. SEXANGULARE(Lund.). (Pl.xiii., f.22). 



Forma senilis, membrana incrassata, Long.40; lat.37; isth.8;^. 



Collector, 



Cos. sexangulare Lund., Desm, Suec. T.ii., f.23. The hexagonal 

 form is not stable, but gradually develops into a higher form. 

 Occasionally, however, it becomes fixed by incrassation, 



36 



