63 



fitting sutures ; umbilical cavity large extending tlie entire 

 length of tlie spire ; aperture unlinown ; ornament not 

 preserved, probably a nearly smooth shell. Length (average) 

 two and a half inches. 



Obs. — In the internal cast the whorls are more convex, and 

 the sutures well defined. (PI. viii.. Fig. o.) 



Under the name of JViso ? danmnii, the late Prof, de Kouinck 

 described* a small shell from the Upper Silurian, probably 

 Wenlock, beds of Yass, possessing the peculiar continuous 

 umbelical tube of the recent and Tertiary genus Niso. We 

 now have from Lilydale a similar although mvich larger shell, 

 possessing the same character. I have made a longitudinal 

 section of a Niso from the Muddy Creek beds in Victoria 

 (PI. ix.j Fig. 1), and a comparison with that of our more 

 ancient fossil, will at once indicate their close resemblance. 

 In the vertical section of both the umbilical tube is visible, 

 and this can also be seen in one of Prof, de Koninck's 

 figures! of the Yass species. There is a like correspondence 

 between the cross sections of the two shells (PI. viii., 

 Figs. 3 & 4), bearing in mind that the section of the recent 

 epecies is near the apex, and that of the fossil near the base. 



Niso is known in time as far back as the Middle or Lower 

 Tertiaries, and its connection with the Palaeozoic forms is 

 continued through the Secondary rocks by the genus Paheouiso, 

 Gemmellaro. 



The material before me is not sufiicieutto enable me to work 

 this species out in its entirety, but I find myself in the same 

 difficiilty as did Prof, de Koninck, in definitely referring So old 

 a form to a recent and comparatively young genus, geologically 

 speaking. I suspect that the ultimate examination of more 

 perfect .specimens will reveal an organization differing from 

 Niso, in which case I would propose for it the name Vetutuba. J 



Family Turbinid^. 



Genus Cvclonema, Hall, 1852. 

 (PaL N. York, ii., p. 89.) 



CyCLOXEMA ? AUSTRALIS, Sp. UOV. 



(PI. ix.. Figs. 4 & 5.) 



;S);. Char. — Shell turbinate, moderatey elongated, much 

 expanded below, — -whorls six, ventricose, the body -whorl 

 disproportionately larger than the others, — aperture more or 

 less circular ; umbilicus not visible ; operculum unknown ; 

 whorls traversed by successive spiral keels, which are always 



* Rech. Foss. Pal. Nouv. GaUes du Sud, 1876, Pts. 1 & 2, p. 127, t. 4, f. 11. 



■\ Loc. cit., f. lie. 



J Vetus, old ; tubus, a tube or pipe. 



