BY G. I. PLAYPAIR. 619 



Cos. genuosum Nord., Frw. Alg. N. Z T.6, f.4; Cos. umbonu- 

 latum Nord., I.e. T.6, f 2; and Cos. variolatum Lund. (3 extensum 

 Nord., I.e. T.6, f.3, have something in common with this form. 

 From them all it differs in its larger size, especially the greater 

 diameter, in its honeycombed membrane and spirally twisted 

 side- and end-views. Raciborski's forma minor, Desm. Ciast. 

 T.l, £.32, is Cos. subbinale (Nord.) Lager. 



Cos. glyptodermum West & West, Frw. Alg. Madag. T.7, f.23. 



Semicellulse semper globosae, a vertice semper circulares. 

 Endochroma interdum in taenias parietales circ. 9, interdum in 

 laminas parietales 4-6 disposita. 



Long. 112-132; lat. 66-78^. 



Coogee(l,4, 13, 24,58). 



Common at Coogee, but not found elsewhere. In the Auburn- 

 Guildford district its place is taken by Cos. tholiforme Cohn, 

 Desm. Bongo, f.9. 



Genus Xanthidium Ehr. 

 Xan. inohoatum Nord. (3 mammillatum, n.var. (Plate xii., fig. 6). 



Paullo majus quam forma typica. Semicellulse hexagonse, basi 

 plana, ad foramen sinus parva verruca praedita, apice lato trun- 

 cato, basi latitudine pari, angulis apicalibus aculeis singulis fere 

 verticalibus munitis; lateribus mammillatis, rectangularibus, 

 parte inferiore levissime retusa, angulis lateralibus rotundatis, 

 A vertice visse semicellulse ellipticse (Cos. obsoleto simillimse sed 

 angustiores), apicibus acuminatis obtuse-rotundatis, utrinque in 

 medio membrana introrsum incrassata. A latere subcirculares, 

 utrinque incrassataB, aculeo sursum praeditse. Membrana achroa, 

 glabra, in centro semicellularum incrassata. 



Long.c.ac. 54-63, sac. 41-45; lat. 42-45; crass. 22-23/x. 



Guildford (23, 45). 



Cf. Xan. inchoatv.m Nord., Frw. Alg. N.Z. T.6, £.30; and Xan. 

 (Eu.) exile Josh., Burm. Desm. T.23, f.16. 



